Moscow, Russia - Armed police officers broke into Nigora Marupova's rented apartment in southeastern Moscow at dawn on May 5 and took away her weeping and screaming daughters aged two and four.

They told the confounded woman from Uzbekistan, who lived in Russia for 14 years without legal trouble, that they would place the children in an orphanage because Marupova had ties to "terrorists" that masterminded the April 3 subway bombing in St Petersburg, Russia's second-largest city and President Vladimir Putin's hometown.

"They took the kids by force," Marupova, a 30-year-old brunette with a pale, haggard face, told Al Jazeera. "They did not want to return the smaller one, wanted to keep the child as a hostage, said she was their insurance."

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No ties whatsoever were found after interrogations, but the children were released days later only after Memorial, one of Russia's oldest and most respected human rights groups, stepped in with a squall of complaints and a threat of legal action.

"This was an abduction," Memorial's Bakhrom Khamroev told Al Jazeera, adding that the raid on Marupova's apartment was part of a sweep on at least 25 buildings in the area where ethnic Uzbeks rented apartments. "One of her girls was registered like she had been found at a junkyard."

Moscow city police and children's protection services refused to discuss Marupova's case.

The sweep was part of a nationwide crackdown on nationals of three ex-Soviet nations of Central Asia - Uzbekistan, Kyrgyzstan and Tajikistan - because the subway bombing that killed 15 and wounded dozens was the first attack carried out in Russia by a Central Asian.

Investigators and security services said Akbarjon Jalilov, a 22-year-old suicide bomber, was behind the attack. An ethnic Uzbek man born in neighbouring Kyrgyzstan, he became a Russian national and worked as a sushi chef and car mechanic. The bespectacled man sported a stylish goatee, not a full beard, and never had ties to armed groups, his friends and relatives told Russian and Kyrgyz media.

Russian investigators claimed he was part of a "sleeping cell" of the Islamic State of Iraq and the Levant (ISIL, also known as ISIS), but the only group that claimed responsibility for the attack was ISIL's sworn enemy. Only three weeks after the attack, the Imam Shamil battalion - a previously unknown, al-Qaeda-linked group in Syria - said Jalilov was its member, according to SITE Intelligence Group, a US company that tracks attacks.

Unwanted migration

Russia sees Central Asia, an arid region strategically stretched between China, Iran and Afghanistan, as its "soft underbelly". Its five nations broke away from the Soviet Union in 1991 and now have a population of more than 60 million.

Three of them - Uzbekistan, Kyrgyzstan and Tajikistan - flooded Russia with millions of labour migrants since the early 2000s. The nations also are the homelands of two dozen suspected accomplices of Jalilov who have been arrested after the bombing, investigators say. Two more were killed while resisting arrest.

Jalilov and his presumed companions are Muslims below 40 who can't boast university degrees or fluent command of Russian and have blue-collar jobs that pay several hundred dollars a month. They also are the living images of Central Asian labour migrants many Russians don't want to live with but the Russian economy can't live without, according to a survey by the Moscow-based Institute for Social Analysis published in mid-May.

"We won't survive without Uzbeks," demographer Yulia Florenskaya wrote in the survey because Russia is losing about a million people of working age a year and has a barely visible growth of the general population of 143 million.

This demographic trend makes the arrival and long-term presence of millions of guest workers inevitable if Russia wants to secure the recovery of its economy hobbled by Western sanctions over Crimea, low oil prices, and cancerous corruption.

Skinheads and cops

Unlike Slavic labour migrants from Ukraine or Belarus that blend in with ethnic Russians, Central Asians have darker skin and hair, different fashion habits and cultural background - including their Muslim faith.

Unsurprisingly, they often attract negative attention - from xenophobic or racist remarks from passersby or neighbours to targeted violence by ultra-nationalists and neo-Nazis. Racially motivated attacks that targeted non-Russians peaked in 2008, when 97 people were killed - including 49 Central Asians - hate crimes monitor Sova said.

One of them was Salokhiddin Azizov, a 20-year-old Tajik labour migrant who was shot and then beheaded by a gang of skinheads who took a photo of his severed head and sent it to journalists. But his brother Jamsheed, who was shot twice by the same gang, returned to Russia after recovering from his wounds.

"There are no jobs to be found in our village," his uncle Rakhmatsho Azizov told this reporter in 2008.

The Kremlin's perennial crackdown on neo-Nazis diminished the number of hate crimes: seven people, including two Central Asians, were killed in 2016, Sova said.

But there is another scourge Central Asians face: the corruption and brutality of police officers who routinely detain them to extort money, rights groups and migrants say.

"If they don't pay up, the police officers get offended and get them deported," Valentina Chupik, head of Tong Jahoni, a Moscow-based human rights group that works with Central Asians, told Al Jazeera. "There is no oppression, there is only a conception of easy prey."

Kremlin's scapegoats?

Under Putin, Russia has seen several waves of government-orchestrated hate campaigns against the nationals of countries that fall out with the Kremlin.

In 2006, after ex-Soviet Georgia declared a pro-Western course, Kremlin-controlled media responded with weeks of hysteria that triggered arbitrary arrests, dismissals, deportations and beatings of ethnic Georgians. In the following years, people from Moldova, Tajikistan, Belarus and Ukraine faced similar abuses in Russia every time their governments disagreed with Moscow.

Russian nationals from the Northern Caucasus region have for years been a magnet of police scrutiny and abuses outside their mostly Muslim region. For more than two decades, Russia has been battling fighters from the Caucasus who were first linked to Chechen separatists and are now joining ISIL.

Several thousand Central Asians have also joined ISIL and other armed groups in Syria, Iraq, and Afghanistan, officials say, and some were labour migrants recruited in Russia. But it was the St Petersburg bombing that made their compatriots a subject of persecution and abuses.

Hundreds, if not thousands, have been deported after the attack, according to Memorial and other rights groups. Official data on 2017 deportations will not be available until early next year.

Some employers suspend or refuse to pay their wages. Some migrants face threats and are told to leave for good. A makeshift mosque was destroyed in a village in the central Tula region, the groups say.

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A Kyrgyz national ended up in a diabetic coma after two days of detention without food and water, and police deported him after he got out of a hospital. An Uzbek woman in labour was not allowed into a maternity ward in the city of Tver and had to give birth at home.

Police did not let another detained Uzbek, a single mother, get in touch with her underage children and locked her up for a night in a basement with bedbugs. A sober Tajik man who does not own a car was sentenced to 10 days in jail for drunk driving.

Some observers think that this is a tried-and-tested Kremlin strategy of diverting attention from domestic problems such as the economic crisis, corruption, opposition and labour protests that has multiplied in recent months.

"This is Kremlin's strategy - 'we're always looking for enemies,'" said Memorial's Khamroev, an ethnic Uzbek whose apartment was searched twice recently and whose laptop was confiscated by police. "Russia faces enormous problems so the public attention is being directed away from them."