"We don't dare talk," members of the Uighur ethnic minority whisper, coming from prayers or as they head out shopping.
One or two who are braver, or more foolish, glance around to scout for eavesdroppers before complaining about how hard it is to find jobs, educate their children or practice their religion.
Xinjiang is nominally autonomous and ruled by the Uighurs - Muslims with Caucasian features who speak a Turkic language - and other ethnic minorities.
But since Mao's troops seized China in 1949 and took control of the region, Beijing has maintained a firm grip on the levers of power and made Uighurs a minority in their own area by encouraging millions of Han Chinese to settle there.
Any incautious criticism of Chinese rule can land a Uighur in prison, exiled activists say.
Only formally incorporated into China in 1884, Xinjiang saw a brief period of virtual independence from 1938 when it sought aid from the Soviet Union - giving added impetus to a 150-year fight for an independent East Turkestan homeland.
But the province is strategically vital to Beijing.
China sees Xinjiang as important
for its oil and coal reserves
It sits on a third of the country's oil and 40% of its coal, accounts for around one-sixth of Chinese territory and gives it a border with several central Asian nations.
Chinese officials say that while tight control is needed to stamp out separatist sentiment and "terrorist ideas" imported from countries such as Afghanistan, the 19-million-strong
population basically lives in harmony.
"Our biggest threat to ethnic relations is Osama bin Ladin and the Taliban," Bai Hua, vice-mayor of the regional capital, Urumqi, told Reuters, waving away suggestions of domestic discontent.
Terrorism fears exploited
But with the last serious violence dating back to the late 1990s - nine died in riots in Yining in 1997 - some say China is exploiting international fears of terrorism.
"China very clearly wants to show the world that it too is a victim of terrorism, to vilify Uighurs' political activities," Dilxat Raxit, the Sweden-based spokesman of the World Uighur Congress, said.
Children under 18 are banned
from attending mosques
He said after the 11 September 2001 attacks on the United States "the Chinese started arresting Uighurs anywhere and for anything ... they did it outside any legal framework".
Even financial success and government praise are no guarantee of immunity from the region's prisons.
Rebiya Kadeer, an exiled businesswoman, was on a consultative body to China's parliament.
But she was detained in 1999 and charged with providing state secrets to foreign institutions after sending newspaper clippings about separatist groups to her husband in the United States.
A network of informants also sows distrust, Uighurs say.
In the border town of Horgas, officials said they rely on their whole population to prevent a repeat of the riots.
"Ordinary people are very vigilant. As soon as they discover some kind of problem, they go straight to the government or public security bureau to report it," Jia Yisheng, a senior party official, told visiting journalists.
But experts say that if Uighurs were allowed to control and enjoy their own culture there would be far less support for secession and Beijing's heavy hand might not be necessary.
Uighur Muslims say China's plan
to help poor regions offers little
"Many Uighurs are more moderate, and would be content with a more autonomous state within China," said one Western diplomat.
China believes an ambitious campaign to develop poorer western regions is bringing Xinjiang the kind of prosperity that countries in Central Asia can only envy. Uighurs say the programme offers little for them.
The influx of Han Chinese - often better educated, better connected and with the language skills to tap into government subsidies - makes it hard for Uighurs to compete.
"The Han work a lot, we just pray a lot," said one man filing out of a run-down small-town mosque.
Mosque, education ban
Most Uighurs are also effectively barred from joining the Communist Party - often a route to improvement in poorer areas of China - by a rule that members must be atheist.
Even for those who do not want to join the party, just observing their faith can be difficult, as the government uses religion to target Uighurs, said Nicolas Becquelin at Human Rights Watch in Hong Kong.
"It is Uighur Islam that is targeted. Through ... control of religion the authorities are trying to quell ethno-nationalist sentiment"
Human Rights Watch
"It is Uighur Islam that is targeted. Through ... control of religion the authorities are trying to quell ethno-nationalist sentiment. Islam is not the real target in this, it is seen as the vehicle for expressing dissent," Becquelin said.
Teaching religion is complicated because children under 18 are banned from attending mosques or receiving religious education, and imams must renew their licence every year and are expected to show patriotism as well as devotion, Becquelin said.
"The mosques look free on the outside," said one nervous shopper. "But on the inside, the pressure is just growing."