China is subjecting the Uighurs, a mostly Muslim ethnic minority in its west, to a crippling amount of surveillance and has reportedly detained up to 2 million of them in internment camps.

Beijing justifies its crackdown as a counterterrorism measure.

Many Western countries have slammed the policy, but China has reportedly been extra keen to mute criticism from Islamic countries.

During a trade trip to China this week — when many lucrative deals were signed — state media recorded Saudi Crown Prince Mohammed bin Salman as saying: "We respect and support China's rights to take counter-terrorism and de-extremism measures to safeguard national security."

His support is significant considering the Saudi royal family's role in the Islamic world as Custodian of the Two Holy Mosques.

Saudi Arabia's crown prince defended China's unprecedented crackdown on up to 2 million Muslims in its western region, likely giving Beijing a big reason to continue a highly controversial policy that activists have likened to "ethnic cleansing" and "precursors to genocide."

The Uighurs, a mostly Muslim ethnic minority living in Xinjiang, are watched by tens of thousands of facial recognition cameras, forced to download surveillance apps on their phones, and not allowed to exhibit Muslim markers like eating halal food or growing a beard.

An estimated 2 million of them, according to US State Department statistics, are locked in internment camps where people are physically and psychologically abused.

Footage purportedly of a re-education camp in Yingye'er, Xinjiang, taken by Bitter Winter magazine in August 2018. Bitter Winter/YouTube

A growing number of Muslim-dominant countries, notably Turkey, have spoken up against the issue to Beijing's ire. But Saudi Arabia, in an effort to boost trade ties, has appeared to turn a blind eye to it.

Read more: The mystery of a Muslim poet who may or may not be dead in a Chinese detention camp is at the center of a diplomatic crisis between China and Turkey

According to China's state-run Xinhua news agency, Crown Prince Mohammed on Friday told Chinese President Xi Jinping: "We respect and support China's rights to take counter-terrorism and de-extremism measures to safeguard national security." He did not mention Xinjiang or Uighurs by name.

Crown Prince Mohammed's comments came during his trade trip to Beijing this week, during which Saudi Arabia and China signed 35 economic-cooperation agreements worth a total of $28 billion at a joint investment forum, according to Saudi state news agency SPA.

Read more: Saudi Arabia and China strike a $10 billion oil deal, brushing off the Khashoggi killing and Xinjiang Muslim camps

Why the crown prince's approval matters

The crown prince's implicit support of China's crackdown in Xinjiang is significant considering his role in the Muslim world.

His father, King Salman, is referred to as the Custodian of the Two Holy Mosques — a deferential title used to acknowledge his responsibility of the two holy cities of Mecca and Medina.

Earlier this week an unnamed Beijing-based diplomat told Reuters that China was keen to head off criticism from Muslim countries about its internment camps.

Crown Prince Mohammed poses with Chinese Ambassador to Saudi Arabia Li Huaxin at the Great Wall of China on Thursday. Riyadh and Beijing signed $28 billion worth of new deals this week, Saudi state media said. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS

While China justifies the oppression as counter-extremism, experts have also cited Xinjiang's proximity to multiple infrastructure projects and Beijing's unwillingness to jeopardize them.

Read more: This map shows a trillion-dollar reason why China is oppressing more than a million Muslims

China also appeared to turn a blind eye to Saudi Arabia's human rights record. Crown Prince Mohammed is widely believed to be responsible for the brutal killing of journalist Jamal Khashoggi, who died at the hands of Saudi agents in the kingdom's consulate in Istanbul last October.

US Senators, and reportedly the CIA, have already pointed the finger at him. But according to China's state-run CCTV news channel, Xi told the crown prince on Friday that China "opposes any moves to interfere in Saudi Arabia's internal affairs."