Suicide pipe bombers made a dozen attacks on police stations, government offices and businesses yesterday as Muslim separatists in the far northwest of China stepped up their Olympics bombing campaign.

At least 11 people died in the raids, which took place before dawn in Kuqa, an oasis city on the northern edge of the Taklimakan desert in the predominantly Muslim region of Xinjiang. Ten of the dead were reported to be attackers, three of whom appear to have blown themselves up to avoid capture.

It was an unprecedented event in China, which has no history of suicide bombing, and a grave escalation of the deteriorating security situation in one of its most tense and isolated areas.

Last night checkpoints sealed off the road to the police headquarters where attackers detonated a wagon filled with explosives at 2.30am, killing a civilian guard and injuring two police. According to the Xinhua news agency, the police fired back, killing one of the attackers and capturing two after a fourth killed himself with his bomb.

Half an hour earlier, an explosion blew out windows in a row of businesses. The owner of one café, where people were drinking at the time of the explosion, said: “Suddenly there was a big bang. The customers and I just ran away. When I looked back, my shop was totally destroyed.”

At 8.30am, police cornered five of the alleged attackers under a market stall. Two were shot dead as they threw their bombs while the other three blew themselves up. There were also attacks on a local government building and the premises of a trade organisation. A curfew was imposed and businesses in Kuqa county were ordered to close as police hunted for attackers, who, said Xinhua, had used bombs made from pipes, gas canisters and containers of liquid gas.

Kuqa is in the northern part of Xinjiang, a vast region of desert and mountainwhere the predominantly Muslim Uighur people are the largest ethnic population. In the months preceding the Olympics there had been increasing activity by separatist organisations seeking to establish an independent Islamic state of “East Turkestan”. Chinese authorities have reported a series of plots, including schemes to kidnap athletes and bomb a domestic flight, while bombs on buses killed five people in southwest China. There were doubts about whether they were serious threats or had been exaggerated by the authorities to justify intense Olympics security measures.

It was only last Monday, when 16 policemen were killed in a knife and bomb attack in the Xinjiang city of Kashgar, that it became clear that the dormant campaign for an independent East Turkestan had been revived.

Shi Dagang, a senior communist party official in Kashgar, said: “They are trying to turn 2008 into a year of mourning for China. I admit that we face a severe campaign because I know that these people will not lose their momentum.”

Two videos, of dubious authenticity, have been posted on the internet by a group claiming responsibility for the bus bombings. The latest, which appeared last Friday, told Muslims to avoid ethnic Chinese - difficult even in Xinjiang, where immigrants from the east almost match the Uighur population in numbers.

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