BEIJING - China's top Communist Party leader in Tibet has said the fight against separatism remains "very serious" more than a year after deadly unrest hit the Himalayan region, state media reported Tuesday.

In a speech in the regional capital Lhasa, Zhang Qingli urged all levels of government, as well as the military, to step up efforts to ensure public order in the Himalayan region hit by deadly unrest in 2008, the Tibet Daily reported.

"Since 2005, we have made important contributions to safeguard overall social stability... by hitting hard and preventing (separatism) and by building a solid line of defence to strike at hostile people," Zhang said.

But, "at present the anti-separatist struggle in our region remains very serious," the paper quoted him as saying this week.

His comments come after a group of exiled former Tibetan political prisoners said last week that Chinese soldiers had executed three Tibetans for their role in anti-Chinese riots in the region in March 2008.

The unrest, which started in Lhasa, spread to other Tibetan-inhabited regions in China, greatly embarrassing the government as it prepared to host the Beijing Olympics.

China has said "rioters" were responsible for 21 deaths, while its security forces killed only one "insurgent". But the exiled Tibetan government has said more than 200 Tibetans were killed in China's subsequent crackdown.

Officials in Lhasa have refused to confirm or deny the executions when contacted repeatedly by AFP.

Chinese state media said in April that two people had been sentenced to death over the unrest, the first such penalties reported.

In his speech, Zhang praised the Tibetan government and people for their handling of the situation.

"We have built an impregnable fortress of people to handle in accordance with the law the serious March 14 violent criminal incident of smashing, looting and burning," Zhang said.

We must "strengthen the management of overall public order, make greater efforts to resolve those prominent issues that influence social order, ensure state security and safeguard social harmony and stability in our region."

China has ruled Tibet since 1951 after sending in troops to "liberate" the Himalayan region the previous year, and Beijing has long maintained that its rule ended a Buddhist theocracy that enslaved all but the religious elite.

Beijing sees Tibet's exiled spiritual leader, the Dalai Lama, as a splittist bent on independence for Tibet, but the Buddhist monk insists he only wants greater regional autonomy.