The Chinese authorities are anxious that mysterious syringe stabbings that have caused panic in the restive far west have now reached the capital.

The threat of such needle attacks comes as an enormous security blanket has been thrown across Beijing to ensure that a huge military parade to celebrate the 60th anniversary of Communist Party rule passes off without a hitch on October 1.

Indications that the bizarre attacks may have extended from the mostly Muslim, riot-torn region of Xinjiang to Beijing came in the form of directives from internet service providers to clients to prevent any mention of such violence on websites.

Managers of websites said that they received notification today to delete any discussion or mention of syringe stabbings in Beijing as soon as these are spotted.

In a country where the media are carefully monitored by the propaganda authorities, the internet has become the most important outlet for relatively free discussion of almost every topic. News often breaks first on smaller sites that have escaped the eagle eye of China’s cyber police.

One website manager, who declined to be identified for fear of retribution, told The Times that he had been given no indication of where or when such attacks might have taken place in Beijing. He said: “We don’t even know what is in the syringes. But I’m not worried. I’ll just make sure I only go out in my car and don’t walk in the streets.”

The attacks in Xinjiang have spread from the capital, Urumqi, where 200 people were killed in July when ethnic Uighurs turned on Han Chinese, to smaller cities in the region where many chafe under Beijing rule.

According to officials more than 600 people in Urumqi say that they have been stabbed, although many incidents have turned out to be nothing more serious than mosquito bites. More than 40 people have been detained in the city in connection with the attacks.

State media said that nine suspects have now been detained in the smaller Silk Road cities of Khotan, Altay and Kashgar.

Such is the level of suspicion in China, where people are accustomed to suppression of news in the state-run media, that rumours can easily set off panic. A police text message ignited the panic last week in Urumqi when tens of thousands of Han Chinese marched through the streets to demand government action to stop the attacks.

The message said: "Recently, several residents were attacked by hypodermic syringes. Local police security departments have also uncovered a case in which assailants used syringes to attack passers-by. Please don't panic over the incident, and inform police officers if you find any suspects." People then panicked.

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