A melee in Tibet's capital appeared to have been sparked by attempts by police to carry out security checks, indicating the tension and volatility remaining in Lhasa weeks after an anti-government riot.

A mobile phone text message to Lhasa residents from the local police said security checks carried out on Saturday had "frightened citizens" and caused panic in the city centre.

"Please obey the law and please follow the rules, don't create rumours, don't believe rumours, don't spread rumours," read the text message, which was reprinted by the Free Tibet Campaign and International Campaign for Tibet.

"Severely battle any creation or any spreading of rumours that would upset or frighten people or cause social disorder or illegal criminal behaviour that could damage social stability," the message read.

It was not clear if the security check was in response to a protest, or if the check itself caused the panic.

"Although full details could not be confirmed, reliable reports indicated that a new protest occurred involving many Tibetans, possibly linked to an attempt by armed police to detain Tibetans ... in central Lhasa," the Washington-based International Campaign for Tibet said in a statement.

The fresh tensions come as China prepares to receive the Olympic flame in its capital Beijing on Monday, for the start of a domestic and international relay that the government hoped would symbolise national unity ahead of the August Games.

Instead, China finds itself deflecting criticism over its policies in Tibet and its response to unrest there, and facing the prospect of weeks of protests as the Olympic flame circles the globe.

The unrest began with days of peaceful, monk-led protests in Lhasa that spiralled into a citywide riot on March 14 that the government says killed 18 civilians and was masterminded by the Dalai Lama, Tibet's spiritual leader.

The Dalai Lama, who fled China in 1959 after a failed uprising against Chinese Communist rule, denies he is behind the unrest, which his representatives say has claimed some 140 lives.

The protests also spread to ethnic Tibetan areas of China. In Sichuan province's Aba county, where police opened fire on protesters a week ago, 26 suspects were detained for their involvement, the state-run Xinhua news agency reported.

Police seized guns, bullets, explosives and knives in Aba's Kirti monastery, as well as Tibetan flags and banners advocating independence for Tibet, the report said.

The Tibet Centre for Human Rights and Democracy, based in India, gave a different account, saying more than 100 monks from the Kirti monastery were detained and that police raided rooms, ransacking portraits of the Dalai Lama.

The paramilitary People's Armed Police erected sandbag barricades around the monastery to stop more protests, it said.

US President George W Bush has urged China to exercise restraint in its response to the unrest and to meet representatives of the Dalai Lama.

A meeting of European Union foreign ministers also called on Saturday for an end to violence in Tibet and urged dialogue on the region's religious and cultural rights. But in a joint text, the bloc avoided reference to the Beijing Games, after a week of public differences over whether to boycott the opening ceremony. - Reuters