At least five people were killed and several more were critically injured in a series of bomb explosions in China's far west region of Xinjiang, in what looks increasingly like a concerted bombing campaign by Muslim separatists to coincide with the Beijing Olympics.

Witnesses described how attackers threw home made bombs at a police station and office buildings, injuring police and security guards and destroying two police cars. Five of the attackers were reported to have been killed at the scene.

The state Xinhua new agency reported a series of explosions between 3.20am and 4am in the oasis town of Kuqa, 2,500 miles west of Beijing in the Taklimakan Desert. "Flashes of fire" and gunshots were reported after the explosions, the report said, and police were hunting for further suspects.

"There were several explosions in several places in the county seat of Kuqa this morning and we heard them from the hospital," a hospital employee named Ms Tian told the Associated Press from Kuqa. She confirmed that one man was pronounced dead upon arrival while others arrived in a critical condition.

Kuqa is in the northern part of Xinjiang, a vast region of deserts and mountains, where the Uighur people, who are predominantly Muslim, are the largest ethnic population. The months preceding the Olympics have seen increasing activity by shadowy separatist organisations who seek to throw off the government of communist China and establish the independent Islamic state of "East Turkistan".

Chinese authorities have reported a series of terrorist plots, including a scheme to kidnap Olympic athletes, an attempt to set off a bomb on a domestic flight, and bombs on buses which killed five people in south-west China. But foreign analysts have expressed doubts as to whether these were serious terrorist threats, or were exaggerated by the Chinese authorities to justify the intense security measures imposed on the country during the Olympics.

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

The local authorities said that the attack was part of an Olympic terrorism campaign. "They are trying to turn 2008 into a year of mourning for China," said Shi Dagang, a senior communist party official in Kashgar. "I admit that we face a severe campaign because I know that these people will not lose their momentum."

"With the special background of the eve of the Beijing Olympic Games, hostile forces at home and abroad will surely act like cornered mad dogs and step up their terror and sabotage activities," said the governor of Xinjiang, Nuer Baikeli, in the provincial newspaper on Friday.

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 just before the opening of the Games, warned Muslims to avoid ethnic Chinese - a difficult task even in Xinjiang, where immigrants from the east of the country almost match the local Uighur population in numbers.

In the video a masked fighter with a rifle stood in front of a burning Olympic symbol, and said: "Do not stay on the same bus, on the same train, on the same plane, in the same buildings, or any place as the Chinese."

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