In their worst nightmares Chinese security forces cannot have believed that an attack of such savagery could occur on home soil. For their part, the attackers cannot have expected that their assault – timed to sow panic before the Olympics begin on Friday – would be so destructive.

It is a decade since the last serious violence involving Muslim Uighur separatists brought deadly results in Xinjiang. Many observers wondered if repeated Chinese warnings in recent months of a serious terrorist threat from the Uighurs were intended merely to justify the extreme security measures for the Olympics.

Western security experts told The Times nearly a year ago that the brewing discontent in the westernmost Chinese region was not to be taken lightly. This has proved to be well grounded.

The two men involved in the incident – identified as Uighurs by the Chinese authorities – doubtless intended their action to gain the maximum attention before the Olympics.

The high level of casualties does not equate to a high level of organisation, however. A previous outburst of violence and bus bombings in the late 1990s resulted in barely a dozen deaths. Chinese authorities arrested dozens of people and executed many, but they gave scant indication that there had been careful organisation by any particular group. It is possible that the attack was carried out by a few individuals seeking revenge against the Chinese.

Wang Lixiong, a Chinese author who has written widely about Xinjiang, said that he was not surprised at the attack but was astonished at the scale. “They would have thought that it would be too difficult to launch an attack on the Olympics in Beijing, but they want to seize the opportunity to attract attention while the eyes of the world are on China,” he said.

Few analysts are expecting Uighur-inspired violence in the Chinese capital. “Even after this we don’t see reason to think there is a dark hand controlling things from behind the scenes,” Andrew Gilholm, of the consultancy Control Risks, said.

It was unlikely that either of the two main overseas groups seeking independence for a region they call East Turkestan would have been involved. The radical East Turkestan Independence Movement has been listed as a terrorist organisation but is believed to have few members. It is thought to include a group called the Turkestan Islamic Party, which released a video last month showing a masked man claiming responsibility for recent bus blasts in China.

Officials in Xinjiang have become increasingly concerned at the reach of an international Sunni group called Hizb ut-Tahrir, or Party of Liberation, whose aim is to set up an Islamic caliphate across Asia and which organised protests in the western city of Khotan in March.

Wang said that the attack appeared to have been carefully planned to target only the police rather than ordinary Chinese – a tactic that could win support among those Uighurs who do not resent their Chinese neighbours but are angered by police repression.

“I think a lot of Uighurs may not be unhappy about this attack. They are also realists: most of them may want independence but most of them know that it is impossible,” he said.

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