Thousands of troops are on the streets of the Tibetan capital Lhasa amid reports of a huge military build-up, as China admitted for the first time it had shot Tibetan protesters over the weekend.

Xinhua, the state run news agency, said that police shot four people in Aba county, an ethnic Tibetan part of the western Sichuan province, on Sunday.

Authorities on Thursday also acknowledged for the first time that anti-government riots had spread from Tibet to other provinces.

Reporters and witnesses said military convoys were on the move in Tibet and troops have been deployed in nearby provinces.  

The latest Chinese crackdown came after violent protests against China's rule of the Himalayan region.

Military convoys

Georg Blume, a German journalist in Lhasa said: "We saw a big convoy of military vehicles with troops in the back."

"One convoy was about two kilometers long and contained about 200 trucks. Each had 30 soldiers on board so that's about 6,000 military personnel in one convoy."

Blume, who works for the German newspaper Die Zeit, said he had seen security forces going from one house to the next.

A week of protests against China's 57-year rule of Tibet erupted into rioting in Lhasa last Friday.

Demonstrations have since spilled over into nearby Chinese provinces with sizeable ethnic Tibetan populations.

China said rioters killed 13 innocent civilians in Lhasa while denying that it used deadly force to end the protests.

Exiled Tibetan leaders say about 100 people have been killed in the Chinese crackdown.

The Dalai Lama, Tibet's spiritual leader, on Thursday expressed concern for the many people he said had fallen victim to Chinese security forces.

"We don't know exact numbers. Some say six, some say 100, but places have been cut off. There are movements of Chinese troops. I am really worried a lot of casualties have happened," he said from exile in northern India.

Xinhua said security forces had shot and wounded four protesters "in self-defense" during protests in the remote county of Aba (known in Tibetan as Ngawa).

Differing casualties

However, activist groups say at least eight people were killed by security forces in the Aba protests.

They circulated photos this week of dead bodies with apparent bullet wounds to back up their allegations that Chinese forces were using lethal force despite official claims to the contrary.

The unrest has been a public relations challenge for China in the lead-up to the Beijing Olympics in August.

While no government has called for a boycott of the Games, China has faced increasing international pressure to resolve the unrest peacefully and to hold talks with the Dalai Lama.

PHOTO CAPTION 

Shop owners clean-up their burnt-out businesses in the Tibetan capital Lhasa.

Al-Jazeera