Chinese are venting their anger online after ethnic violence in the Muslim region of Xinjiang left at least 156 dead but are playing a cat-and-mouse game with censors who appear to be removing some posts and blogs.

Many of the comments demanded swift punishment for those involved, echoing remarks in official state media blaming exiled Uighur activist Rebiya Kadeer for masterminding the riots in the regional capital of Urumqi on Sunday.

Destroy the conspiracy, strike hard against these saboteurs, and strike even more fiercely than before, said an anonymous posting on a blog on www.sina.com.cn by a person known as Chang Qing.

Yet authorities have been working fast to remove comments about the violence, apparently to prevent ethnic hatred from spreading or Internet users questioning government policies toward regions populated by ethnic minorities.

Along with Tibet, Xinjiang is one of the most politically sensitive regions in China and Beijing has tried to control online debate about the violence across China.

Many blogs have simply posted articles from the domestic media about the unrest, but in the section where readers are invited to leave their thoughts is written: There are no comments at this time -- unusual, given the popularity of blogs in China with 300 million Internet users.

Some sites which had posted graphic images of beaten and bloody bodies, purportedly taken during or after the riots, also had them swiftly removed.

The government has cut access to the Internet in Urumqi, the city's Communist Party Chief Li Zhi said on Tuesday, to stop it being used to fuel further violence.

Also on Tuesday, access to social networking site Facebook seemed to be disrupted in some places. Users in Guangzhou Shanghai, Beijing and Chongqing said they could not reach the site, although Facebook spokesman Larry Yu said the company was not seeing any changes in traffic from China at this time.

This came on top of an apparent block on Twitter and search restrictions for Xinjiang topics on Chinese rival, Fanfou.com.

REVENGE VS UNDERSTANDING

Almost half of Xinjiang's 20 million people are Uighurs, a Turkic, largely Islamic people who share linguistic and cultural bonds with Central Asia.

They have long complained Han Chinese reap most of the benefits from official investment and subsidies, while making Uighurs feel like outsiders.

Postings showed a mixture of suspicion and sympathy for Uighurs in the wake of violence that critics have called a separatist plot, but overseas activists have said was a spontaneous outpouring of long-standing grievances.

Some warned Hans, China's predominant ethnic group, would take revenge -- shortly before thousands of angry Han protestors took to the streets of Urumqi seeking Uighur targets.

The blood debt will be repaid. Han compatriots unite and rise up, wrote Jason on search engine www.baidu.com.

Others have sought to invoke the spirit of Wang Zhen, the Chinese general who is reviled and feared by many Uighurs for repression when he led Communist troops into Xinjiang in 1949 to bring it into the newly formed People's Republic of China.

Study this hard, wrote one posting above a potted history of Wang apparently taken from a Chinese history book.

Still, a few people appealed for greater understanding of Uighur grievances.

If your family members have no rights, no power, are discriminated against and made fun of, not only will your family collapse, you will already have sown the seeds of hatred, wrote Bloody Knife.

One person, called zfc883919 and writing on Xinjiang portal www.tianya.cn, said he did not understand how the police could have let the death toll rise so high.

What on earth were you doing? That was 156 living beings. I hope relevant authorities really learn a lesson, so that this kind of tragedy is not repeated.

(Additional reporting and writing by Emma Graham-Harrison; Editing by Benjamin Kang Lim and Sophie Hares)