BEIJING, March 17, 2008 (AFP) - China on Monday urged foreigners not to travel to Tibet, with reports authorities were trying to seal off the Himalayan region amid a crackdown on anti-Chinese protests.

"Because of the arson and murders which have taken place in Tibet, we do not advise foreign news organisations or foreign nationals to go to Tibet for safety reasons," the chairman of Tibet's government, Qiangba Puncog, told reporters at a hastily called news conference in Beijing.

Qiangba, who is in the capital for the annual session of the national legislature, had been asked to respond to reports that foreigners were being ordered from the region.

He said "foreign companies" had not been asked to leave so far but provided no other details.

Tour operators have told AFP that foreigners seeking entry to Tibet were being denied necessary permits in the aftermath of a week of violence there.

Foreign tourists also said they had flown into Lhasa on Friday and Saturday, the apparent peak of the unrest, but were not allowed into the city and ordered back on a flight out of Tibet.

Meanwhile, there was no response from authorities to requests by foreign news organisations for permission to report in Tibet.

Despite the lack of access for foreigners, media organisations have determined that there is a massive security force of Chinese police and People's Liberation Army in Lhasa.

Tibet's government-in-exile said on the weekend that 80 Tibetans had been confirmed killed in the crackdown by the Chinese forces, and that possibly more than 100 had died.

Qiangba said that Tibetan rioters had killed 13 "innocent civilians" but denied using lethal force to quell the unrest.

The violence has posed a huge crisis for China as it builds up to the August Olympic Games amid growing pressure over Beijing's 57-year control of Tibet, human rights and other issues.