Nobody knows what happened to the Uighur student after he returned to China from Egypt and was taken away by police.

Not his village neighbours in China's far west, who haven't seen him in months. Not his former classmates, who fear Chinese authorities beat him to death.

Not his mother, who lives in a two-story house at the far end of a country road, alone behind walls bleached by the desert sun. She opened the door one afternoon for an unexpected visit by AP reporters, who showed her a picture of a handsome young man posing in a park, one arm in the wind.

"Yes, that's him," she said as tears began streaming down her face. "This is the first time I've heard anything of him in seven months. What happened?"

"Is he dead or alive?"

The student's friends think he joined the thousands — possibly tens of thousands — of people, rights groups and academics estimate, who have been spirited without trial into secretive detention camps for alleged political crimes that range from having extremist thoughts to merely travelling or studying abroad. The mass disappearances, beginning the past year, are part of a sweeping effort by Chinese authorities to use detentions and data-driven surveillance to impose a digital police state in the region of Xinjiang and over its Uighurs, a 10-million strong, Turkic-speaking Muslim minority that China says has been influenced by Islamic extremism.

Along with the detention camps, unprecedented levels of police blanket Xinjiang's streets. Cutting-edge digital surveillance systems track where Uighurs go, what they read, who they talk to and what they say. And under an opaque system that treats practically all Uighurs as potential terror suspects, Uighurs who contact family abroad risk questioning or detention.

The campaign has been led by Chen Quanguo, a Chinese Communist Party official, who was promoted in 2016 to head Xinjiang after subduing another restive region — Tibet. Chen vowed to hunt down Uighur separatists blamed for attacks that have left hundreds dead, saying authorities would "bury terrorists in the ocean of the people's war and make them tremble."

Through rare interviews with Uighurs who recently left China, a review of government procurement contracts and unreported documents, and a trip through southern Xinjiang, the AP pieced together a picture of Chen's war that's ostensibly rooting out terror — but instead instilling fear.

Most of the more than a dozen Uighurs interviewed for this story spoke on condition of anonymity for fear that Chinese authorities would punish them or their family members. The AP is withholding the student's name and other personal information to protect people who fear government retribution.

World news in pictures Show all 50 1 /50 World news in pictures World news in pictures 14 September 2020 Japan's Prime Minister Shinzo Abe, Chief Cabinet Secretary Yoshihide Suga, former Defense Minister Shigeru Ishiba and former Foreign Minister Fumio Kishida celebrate after Suga was elected as new head of the ruling party at the Liberal Democratic Party's leadership election in Tokyo Reuters World news in pictures 13 September 2020 A man stands behind a burning barricade during the fifth straight day of protests against police brutality in Bogota AFP via Getty World news in pictures 12 September 2020 Police officers block and detain protesters during an opposition rally to protest the official presidential election results in Minsk, Belarus. Daily protests calling for the authoritarian president's resignation are now in their second month AP World news in pictures 11 September 2020 Members of 'Omnium Cultural' celebrate the 20th 'Festa per la llibertat' ('Fiesta for the freedom') to mark the Day of Catalonia in Barcelona. Omnion Cultural fights for the independence of Catalonia EPA World news in pictures 10 September 2020 The Moria refugee camp, two days after Greece's biggest migrant camp, was destroyed by fire. Thousands of asylum seekers on the island of Lesbos are now homeless AFP via Getty World news in pictures 9 September 2020 Pope Francis takes off his face mask as he arrives by car to hold a limited public audience at the San Damaso courtyard in The Vatican AFP via Getty World news in pictures 8 September 2020 A home is engulfed in flames during the "Creek Fire" in the Tollhouse area of California AFP via Getty World news in pictures 7 September 2020 A couple take photos along a sea wall of the waves brought by Typhoon Haishen in the eastern port city of Sokcho AFP via Getty World news in pictures 6 September 2020 Novak Djokovic and a tournament official tends to a linesperson who was struck with a ball by Djokovic during his match against Pablo Carreno Busta at the US Open USA Today Sports/Reuters World news in pictures 5 September 2020 Protesters confront police at the Shrine of Remembrance in Melbourne, Australia, during an anti-lockdown rally AFP via Getty World news in pictures 4 September 2020 A woman looks on from a rooftop as rescue workers dig through the rubble of a damaged building in Beirut. A search began for possible survivors after a scanner detected a pulse one month after the mega-blast at the adjacent port AFP via Getty World news in pictures 3 September 2020 A full moon next to the Virgen del Panecillo statue in Quito, Ecuador EPA World news in pictures 2 September 2020 A Palestinian woman reacts as Israeli forces demolish her animal shed near Hebron in the Israeli-occupied West Bank Reuters World news in pictures 1 September 2020 Students protest against presidential elections results in Minsk TUT.BY/AFP via Getty World news in pictures 31 August 2020 The pack rides during the 3rd stage of the Tour de France between Nice and Sisteron AFP via Getty World news in pictures 30 August 2020 Law enforcement officers block a street during a rally of opposition supporters protesting against presidential election results in Minsk, Belarus Reuters World news in pictures 29 August 2020 A woman holding a placard reading "Stop Censorship - Yes to the Freedom of Expression" shouts in a megaphone during a protest against the mandatory wearing of face masks in Paris. Masks, which were already compulsory on public transport, in enclosed public spaces, and outdoors in Paris in certain high-congestion areas around tourist sites, were made mandatory outdoors citywide on August 28 to fight the rising coronavirus infections AFP via Getty World news in pictures 28 August 2020 Japanese Prime Minister Shinzo Abe bows to the national flag at the start of a press conference at the prime minister official residence in Tokyo. Abe announced he will resign over health problems, in a bombshell development that kicks off a leadership contest in the world's third-largest economy AFP via Getty World news in pictures 27 August 2020 Residents take cover behind a tree trunk from rubber bullets fired by South African Police Service (SAPS) in Eldorado Park, near Johannesburg, during a protest by community members after a 16-year old boy was reported dead AFP via Getty World news in pictures 26 August 2020 People scatter rose petals on a statue of Mother Teresa marking her 110th birth anniversary in Ahmedabad AFP via Getty World news in pictures 25 August 2020 An aerial view shows beach-goers standing on salt formations in the Dead Sea near Ein Bokeq, Israel Reuters World news in pictures 24 August 2020 Health workers use a fingertip pulse oximeter and check the body temperature of a fisherwoman inside the Dharavi slum during a door-to-door Covid-19 coronavirus screening in Mumbai AFP via Getty World news in pictures 23 August 2020 People carry an idol of the Hindu god Ganesh, the deity of prosperity, to immerse it off the coast of the Arabian sea during the Ganesh Chaturthi festival in Mumbai, India Reuters World news in pictures 22 August 2020 Firefighters watch as flames from the LNU Lightning Complex fires approach a home in Napa County, California AP World news in pictures 21 August 2020 Members of the Israeli security forces arrest a Palestinian demonstrator during a rally to protest against Israel's plan to annex parts of the occupied West Bank AFP via Getty World news in pictures 20 August 2020 A man pushes his bicycle through a deserted road after prohibitory orders were imposed by district officials for a week to contain the spread of the Covid-19 in Kathmandu AFP via Getty World news in pictures 19 August 2020 A car burns while parked at a residence in Vacaville, California. Dozens of fires are burning out of control throughout Northern California as fire resources are spread thin AFP via Getty World news in pictures 18 August 2020 Students use their mobile phones as flashlights at an anti-government rally at Mahidol University in Nakhon Pathom. Thailand has seen near-daily protests in recent weeks by students demanding the resignation of Prime Minister Prayut Chan-O-Cha AFP via Getty World news in pictures 17 August 2020 Members of the Kayapo tribe block the BR163 highway during a protest outside Novo Progresso in Para state, Brazil. Indigenous protesters blocked a major transamazonian highway to protest against the lack of governmental support during the COVID-19 novel coronavirus pandemic and illegal deforestation in and around their territories AFP via Getty World news in pictures 16 August 2020 Lightning forks over the San Francisco-Oakland Bay Bridge as a storm passes over Oakland AP World news in pictures 15 August 2020 Belarus opposition supporters gather near the Pushkinskaya metro station where Alexander Taraikovsky, a 34-year-old protester died on August 10, during their protest rally in central Minsk AFP via Getty World news in pictures 14 August 2020 AlphaTauri's driver Daniil Kvyat takes part in the second practice session at the Circuit de Catalunya in Montmelo near Barcelona ahead of the Spanish F1 Grand Prix AFP via Getty World news in pictures 13 August 2020 Soldiers of the Brazilian Armed Forces during a disinfection of the Christ The Redeemer statue at the Corcovado mountain prior to the opening of the touristic attraction in Rio AFP via Getty World news in pictures 12 August 2020 Young elephant bulls tussle playfully on World Elephant Day at the Amboseli National Park in Kenya AFP via Getty World news in pictures 11 August 2020 French Prime Minister Jean Castex is helped by a member of staff to put a protective suit on prior to his visit at the CHU hospital in Montpellier AFP via Getty World news in pictures 10 August 2020 Locals harvest their potatoes as Mount Sinabung spews volcanic ash in Karo, North Sumatra province, Indonesia Antara Foto/Reuters World news in pictures 9 August 2020 Doves fly over the Peace Statue at Nagasaki Peace Park during the memorial ceremony held for the 75th anniversary of the atomic bombing EPA World news in pictures 8 August 2020 Anti-government protesters try to remove concrete wall that installed by security forces to prevent protesters reaching the Parliament square, during a protest against the political elites and the government after this week's deadly explosion in Beirut AP World news in pictures 7 August 2020 A protester throws a stone towards Israeli forces in the village of Turmus Aya, north of Ramallah in the occupied West Bank, following a march by Palestinians against the building of Israeli settlements AFP via Getty World news in pictures 6 August 2020 A woman yells as soldiers block a road for French President Emmanuel Macron's visit the Gemmayzeh neighborhood. The area in Beirut suffered extensive damage from the explosion at the seaport AP World news in pictures 5 August 2020 Damage at the site of Tuesday's blast in Beirut's port area, Lebanon Reuters World news in pictures 4 August 2020 A large explosion in the Lebanese capital Beirut. The blast, which rattled entire buildings and broke glass, was felt in several parts of the city AFP via Getty World news in pictures 3 August 2020 A general view shows the new road bridge in Genoa, Italy ahead of its official inauguration, after it was rebuilt following its collapse on August 14, 2018 which killed 43 people Reuters World news in pictures 2 August 2020 Empty stall spaces are seen hours before a citywide curfew is introduced in Melbourne, Australia EPA World news in pictures 1 August 2020 People take part in a demonstration by the initiative "Querdenken-711" with the slogan "the end of the pandemic - the day of freedom" to protest against the current measurements to curb the spread of COVID-19 in Berlin, Germany AFP via Getty World news in pictures 31 July 2020 Pilgrims circumambulating around the Kaaba, the holiest shrine in the Grand mosque in Mecca. Muslim pilgrims converged today on Saudi Arabia's Mount Arafat for the climax of this year's hajj, the smallest in modern times and a sharp contrast to the massive crowds of previous years Saudi Ministry of Media/AFP World news in pictures 30 July 2020 The Mars 2020 Perseverance mission lifts off at the Kennedy Space Centre in Florida. The mission is part of the USA's largest moon to Mars exploration. Nasa will attempt to establish a sustained human presence on and around the moon by 2028 through their Artemis programme EPA World news in pictures 29 July 2020 A woman refreshes herself in a outdoor pool in summer temperatures in Ehingen, Germany dpa via AP World news in pictures 28 July 2020 Malaysia's former prime minister Najib Razak speaks to the media after he was found guilty in his corruption trial in Kuala Lumpur AFP via Getty World news in pictures 27 July 2020 North Korean leader Kim Jong Un poses for a photograph after conferring commemorative pistols to leading commanding officers of the armed forces on the 67th anniversary of the "Day of Victory in the Great Fatherland Liberation War". Which marks the signing of the Korean War armistice KCNA via Reuters

Chen and the Xinjiang regional government did not respond to repeated requests for comment. But China's government describes its Xinjiang security policy as a ‘strike hard’ campaign that's necessary following a series of attacks in 2013 and 2014, including a mass knifing in a train station that killed 33. A Hotan city propaganda official, Bao Changhui, told the AP: "If we don't do this, it will be like several years ago — hundreds will die."

China also says the crackdown is only half the picture. It points to decades of heavy economic investment and cultural assimilation programmes and measures like preferential college admissions for Uighurs.

Officials say the security is needed now more than ever because Uighur militants have been fighting alongside Islamic extremists in Syria. But Uighur activists and international human rights groups argue that repressive measures are playing into the hands of the likes of al-Qaida, which has put out Uighur-language recruiting videos condemning Chinese oppression.

"So much hate and desire for revenge are building up," said Rukiye Turdush, a Uighur activist in Canada. "How does terrorism spread? When people have nowhere to run."

The government has referred to its detention program as ‘vocational training,’ but its main purpose appears to be indoctrination. A memo published online by the Xinjiang human resources office described cities, including Korla, beginning ‘free, completely closed-off, militarised’ training sessions in March that last anywhere from 3 months to 2 years.

Uighurs study Mandarin, law, ethnic unity, de-radicalisation, patriotism and abide by the ‘five togethers’ — live, do drills, study, eat and sleep together.

In a rare state media report about the centres, a provincial newspaper quoted a farmer who said after weeks of studying inside he could spot the telltale signs of religious extremism by how a person dressed or behaved and also profess the Communist Party's good deeds. An instructor touted their "gentle, attentive" teaching methods and likened the centres to a boarding school dorm.

But in Korla, the institutions appeared more daunting, at least from the outside. The city had three or four well-known centres with several thousand students combined, said a 48-year-old local resident from the Han ethnic majority. One centre the AP visited was, in fact, labelled a jail. Another was downtown on a street sealed off by rifle-toting police. A third centre, the local Han resident said, was situated on a nearby military base.

While forced indoctrination has been reported throughout Xinjiang, its reach has been felt far beyond China's borders.

In April, calls began trickling into a Uighur teacher's academy in Egypt, vague but insistent. Uighur parents from a few towns were pleading with their sons and daughters to return to China, but they wouldn't say why.

"The parents kept calling, crying on the phone," the teacher said.

Chinese authorities had extended the scope of the program to Uighur students abroad. And Egypt, once a sanctuary for Uighurs to study Islam, began deporting scores of Uighurs to China.

Sitting in a restaurant outside Istanbul where many students had fled, four recounted days of panic as they hid from Egyptian and Chinese authorities. One jumped out a window running from police. Another slept in a car for a week. Many hid with Egyptian friends.

"We were mice, and the police were cats," said a student from Urumqi, Xinjiang's regional capital.

All who returned were intensely grilled about what they did in Egypt and viewed as potential terror suspects, the students said. Many were believed held in the new indoctrination camps, while some were sentenced to longer prison sentences.

The young man from Korla rarely went out in the two years he spent studying Islam in Egypt. He played some soccer — a beloved sport among Uighurs — but wasn't particularly athletic or popular.

Instead, he kept to himself in an apartment that he kept fastidiously clean, steeped in his studies at the revered Al Azhar University, the 1,000-year-old seat of learning in Sunni Islam. He freely discussed Quranic verses with his Uighur friends but mostly avoided politics, one friend said. He spoke of one day pursuing a PhD in comparative religion.

"He had big dreams," said the friend who is now hiding in Turkey to avoid being sent to China. "He wanted to be a religious scholar, which he knew was impossible in China, but he also wanted to stay close to his mother in Korla."

He was fluent in Arabic and but also in Chinese. When they huddled around a smartphone to watch a Taiwanese tear-jerker about a boy separated from his mother, he would be the one weeping first.

When homesickness got to him, he would tell his friends about how his mother doted on him, and about Korla and the big house he grew up in. And when he gets married, God willing, he would say, he'd start a family in that house, too.

"If my wife doesn't agree, then we don't marry," he declared.

He returned to China when he was called back in 2016 and taken away in February, according to three students and a teacher from Cairo. They say they heard from reliable sources in China — but cannot prove — that he died in detention.

Southern Xinjiang, the vast desert basin from where many of the students came, is one of the most heavily policed places on earth.

Deep in the desert's southern rim, the oasis town of Hotan is a microcosm of how Chen, the Xinjiang party boss, has combined fearsome optics with invisible policing.

He has ordered police depots with flashing lights and foot patrols be built every 500 meters (yards) – a total of 1,130, according to the Hotan government. The AP saw cavalcades of more than 40 armoured vehicles including full personnel carriers rumble down city boulevards. Police checkpoints on every other block stop cars to check identification and smartphones for religious content.

Shopkeepers in the thronging bazaar don mandatory armoured vests and helmets to sell hand-pulled noodles, tailored suits and baby clothes.

Xinjiang's published budget data from January to August shows public security spending this year is on track to increase 50 per cent from 2016 to roughly 45 billion yuan ($6.8 billion) after rising 40 per cent a year ago. It's quadrupled since 2009, a watershed year when a Uighur riot broke out in Xinjiang, leaving nearly 200 members of China's Han ethnic majority dead, and security began to ratchet up.

Adrian Zenz, a researcher at the European School of Culture and Theology who tracks Chinese public security staffing levels based on its recruiting ads, says Xinjiang is now hiring 40 times more police per capita than populous Guangdong Province.

"Xinjiang has very likely exceeded the level of police density seen in East Germany just before its collapse," Zenz said. "What we've seen in the last 12 to 14 months is unprecedented."

But much of the policing goes unseen.

To enter the Hotan bazaar, shoppers first pass through metal detectors and then place their national identification cards on a reader while having their face scanned.

The facial scanner is made by China Electronics Technology Group (CETC), a state-owned defence contractor that has spearheaded China's fast-growing field of predictive policing with Xinjiang as its test bed. The AP found 27 CETC bids for Xinjiang government contracts, including one soliciting a facial recognition system for facilities and centres in Hotan Prefecture.

Hours after visiting the Hotan bazaar, AP reporters were stopped outside a hotel by a police officer who said the public security bureau had been remotely tracking the reporters' movements.

"There are tens of thousands of cameras here," said the officer, who gave his name as Tushan. "The moment you took your first step in this city, we knew."

The government's tracking efforts have extended to vehicles, genes, and even voices. In February, authorities in Xinjiang's Bayingol prefecture, which includes Korla, required every car to install GPS trackers for real-time monitoring. And since late last year, Xinjiang authorities have required health checks to collect the population's DNA samples. In May, a regional police official told the AP that Xinjiang had purchased $8.7 million in DNA scanners — enough to analyse several million samples a year.

In one year, Kashgar Prefecture, which has a population of 4 million, has carried out mandatory checks for practically its entire population, said Yang Yanfeng, deputy director of Kashgar's propaganda department. She characterised the check-ups as a public health success story, not a security measure.

"We take comprehensive blood tests for the good of the people, not just record somebody's height and weight," Yang said. "We find out health issues in citizens even they didn't know about."

A biometric data collection program appears to have been formalised last year under "Document No. 44," a regional public security directive to "comprehensively collect three-dimensional portraits, voiceprints, DNA and fingerprints." The document's full text remains secret, but the AP found at least three contracts referring to the 2016 directive in recent purchase orders for equipment such as microphones and voice analysers.

Meiya Pico, a security and surveillance company, has won 11 bids in the last six months alone from local Xinjiang jurisdictions. It won a joint bid with a DNA analysis company for 4 million yuan ($600,000) in Kargilik and has sold software that automatically scans smartphones for "terror-related pictures and videos" to Yarkent.

Meiya and CETC declined comment.

To monitor Xinjiang's population, China has also turned to a familiar low-tech tactic: recruiting the masses.

When a Uighur businessman from Kashgar completed a six-month journey to flee China and landed in the United States with his family in January, he was initially ecstatic. He tried calling home, something he hadn't done in months to spare his family unwanted police questioning.

His mother told him his four brothers and his father were in prison because he fled China. She was spared only because she was frail.

Since 2016, local authorities had assigned ten families including theirs to spy on one another in a new system of collective monitoring, and those families had also been punished because he escaped. Members from each were sent to re-education centres for three months, he told the AP.

"It's worse than prison," he said. "At least in prison you know what's happening to you. But there you never know when you get accused. It could be anytime."

A document obtained by U.S.-based activists and reviewed by the AP show Uighur residents in the Hebei Road West neighbourhood in Urumqi, the regional capital, being graded on a 100-point scale. Those of Uighur ethnicity are automatically docked 10 points. Being aged between 15 and 55, praying daily, or having a religious education, all result in 10 point deductions.

In the final columns, each Uighur resident's score is tabulated and checked ‘trusted,’ ‘ordinary,’ or ‘not trusted.’ Activists say they anecdotally hear about Uighurs with low scores being sent to indoctrination.

At the neighbourhood police office, a woman who gave her surname as Tao confirmed that every community committee in Urumqi, not just Hebei Road West, needed to conduct similar assessments. She said there were no statistics on how many residents had been deemed ‘not trusted,’ nor were there official procedures to deal with them.

"What is happening is every single Uighur is being considered a suspect of not just terrorism but also political disloyalty," said Maya Wang, a researcher at Human Rights Watch who is studying how Chinese police are using technology to track political dissidents as well as Uighurs.

This month, Xinjiang announced it would require every government employee in the region to move into a Uighur home for a week to teach families about ideology and avoiding extremism.

What pains most, Uighurs abroad say, is the self-imposed barrier of silence that separates them from loved ones, making efforts to say happy birthday or find out whether a relative is detained risky.

When Salih Hudayar, an American Uighur graduate student, last called his 70-something grandfather this summer, he spoke in cryptic but reassuring tones.

"Our phones will not work anymore," his grandfather said. "So, don't try calling and don't worry about us. We'll be fine as long as you're all fine."

He later heard from a cousin in Kyrgyzstan that his grandfather had been sent to re-education.

A Uighur student who moved to Washington following the crackdown this summer said that after his move, his wife, a government worker still in Urumqi, messaged to say the police would show up at her home in 20 minutes. She had to say goodbye: after that she would delete him permanently from her contacts list.

A month later he received calls on WhatsApp from a man who introduced himself as Ekber, a Uighur official from the international cooperation office of the Xinjiang regional public security bureau, who wanted him to work for them in the U.S. — and warned him against saying no.

"If you're not working for us then you're working for someone else. That's not a road you want to take," he snapped.

A week after that, he couldn't help himself placing one last call home. His daughter picked up.

"Mom is sick but she doesn't want me to speak to you. Goodbye," she said.

For the past year, Chen's war has meant mass detentions, splintered families, lives consumed by uncertainty. It has meant that a mother sometimes can't get an answer a simple question about her son: is he dead or alive?

A short drive from Korla, beyond peach plantations that stretch for miles, the al-Azhar student's mother still lives in the big house that he loved. When the AP arrived unannounced, she said she had not received any court notices or reasons about why her son and his father were suddenly taken months earlier. She declined an interview.

"I want to talk, I want to know," she said through a translator. "But I'm too afraid."

AP reporters were later detained by police, interrogated for 11 hours, and accused of "illegal reporting" in the area without seeking prior permission from the Korla government.

"The subjects you're writing about do not promote positive energy," a local propaganda official explained.

Five villagers said they knew authorities had taken away the young student; one said he was definitely alive, the others weren't sure.

When asked, local police denied he existed at all.