BEIJING, Aug 11, 2008 (AFP) - China's northwest is seeing its biggest spike in violence in years as Muslim separatists seek to upstage the Olympics, but there is little threat they can hit the Games directly, analysts said.

Militants have staged two attacks in the Xinjiang region over the past week which, although they involved unsophisticated techniques such as exploding small home-made bombs and driving a truck into police, left 27 people dead.

Amid the violence, authorities in Xinjiang said for the first time that 18 foreign terrorists had been captured there this year, on top of previously announced raids that netted over 80 local militants.

"There is an uptick in militant violence in Xinjiang due to the Olympics."

Xinjiang is a vast desert region bordering Central Asia that is home to 8.3 million members of the Muslim ethnic Uighur group, many of whom say they have suffered decades of political and religious repression under Chinese rule.

The Uighurs established two short-lived East Turkestan republics in Xinjiang in the 1930s and 1940s, when Chinese central government control was weakened by civil war and Japanese invasion.

Tensions have simmered over the decades but Bequelin and other experts say such deadly attacks as over the past week have not been seen since the late 1990s.

Chinese authorities have branded those involved in both of the past week's attacks as Uighur "terrorists".

It gave few other details but China has also blamed Uihgur militants for a series of incidents this year, including an alleged attempt by a Uighur woman to blow up a plane flying from the Xinjiang capital Urumqi to Beijing in March.

The warnings were underlined by recent video messages from the Turkestan Islamic Party claiming responsibility for bus explosions this year in Shanghai and the southwestern city of Kunming that killed five people.

The previously little known Turkestan Islamic Party is believed to be closely associated with Xinjiang's East Turkestan Islamic Movement (ETIM), which is listed by China and the United Nations as a terrorist organisation.

None of this year's attacks have come close to Beijing, however, which is thousands of kilometres (miles) from Xinjiang, and intense Chinese security looks likely to keep it that way, said Singapore-based Rohan Gunaratna, head of the International Centre for Political Violence and Terrorism Research.

"The target of ETIM is actually the Beijing Olympics but it is very difficult for them to attack the Games because of the security measures," said Gunaratna.

The ETIM has also shown no ability to conduct large, sophisticated operations, unlike Al-Qaeda and terrorist organisations in other countries.

Nevertheless, despite the security and the militants' rudimentary tactics, the two latest Xinjiang attacks suggest an ability to carry out a small-scale co-ordinated terror campaign, according to Gunaratna.

"What the latest attacks show is that there is significant coordination of these attacks by ETIM forces in (Pakistan's border regions)," he said.

China will likely respond by crushing the militants with a new burst of repression, but that may be what the militants want, said Richard Rigby, a China expert at the Australian National University.

"That's the mistake China has often made in the past, they respond with methods that strengthen the hand of the violent by increasing militant sentiment," he said.

If the militant threat was confined to within Chinese borders, Beijing would likely snuff it out quickly, Gunaratna said.

But the documented presence of a "headquarters" for Uighur militants, out of reach along the Pakistan-Afghan border, means China probably faces a sustained threat of militant violence in Xinjiang, he added.