The attack, which China said was carried out by two Uighur men, was among a string of deadly assaults carried out against government, police and security personnel in north-west China's tense Xinjiang region before and during the Beijing Olympics. At least 26 people were killed in a 10-day period.

Those arrested include people who came to Kashgar from surrounding counties and towns, said Dilxat Raxit, spokesman for the Munich-based World Uyghur Congress.

Some of the detained were beaten and had wounds to their head and legs, Raxit said, citing local sources.

One Kashgar official contacted by Deutsche Presse-Agentur dpa Thursday said: "There weren't that many people arrested," but refused to elaborate. Another official said he was not aware of the situation.

Meanwhile, Kashgar's Shule county government has shut down its website after it was hacked. The flag used by Uighur separatists to represent an independent state of East Turkestan was posted on the website, along with a message calling for independence, the Uighur group said.

The website was inaccessible Thursday, but local officials could not be reached to comment.

The exiled Uighur group also released a copy of a bulletin it said it obtained revealing that the Kashgar government has called for a stepped up campaign against Uighurs following a meeting Monday by local officials to "stabilize the situation."

The bulletin called for stepping up surveillance and control, including focusing on people who are loners, secretive in their speech or actions or are devout Muslims, including those who go outside their community for religious services.

"At roadside checkpoints into Kashgar, they pay special attention to people who appear religious, including men with beards and women who wear head scarfs," said Raxit.

The bulletin also calls for stepping up patrols of neighbourhoods and monitoring of religious activities.

The number of people arrested will likely go up, Raxit said, urging the international community to adopt a more effective and concrete plan to pressure Beijing to stop "trampling on" Uighurs' rights.

Human rights groups have criticized China for not making a distinction between violent terrorists and Uighurs expressing peaceful dissent, including those who favour independence, which they said should not be a crime.

Earlier the Uighur group said about 90 people were arrested following a series of bombings in Kuqa county on August 10. Ten "terrorists" were killed by police bullets or their own bombs, the government said. (dpa)