Where maroon-robed Tibetan monks would clap their hands and shout in spirited Buddhist debate daily, now only birdsong can be heard. Barely a dozen tourists a day visit Sera monastery on the edge of Lhasa and the monks are nowhere to be seen. Many are confined to their quarters. Some have even been arrested.

Shopkeepers in the Tibetan capital are struggling to do business since visitors stopped arriving and a huge police presence deters locals from going out unless they must. Tibet, and its capital, resemble regions under siege since the March 14 riot when citizens angry at Beijing's rule rampaged in the streets, attacking ethnic Han Chinese.

The anti-Chinese violence was just the latest to erupt in Tibetan regions since the Communist Party came to power in China in 1949. In 1989 martial law was imposed on Lhasa for 14 months after troops were sent in to shoot Tibetans as they set fire to shops and businesses owned by Han Chinese.

It was a fateful decision by Hu Jintao, the region's party chief. He is now the President of China and Communist Party chief, and bureaucrats who administer Tibet do not dare to be seen as any less tough on anti-Chinese violence than their boss was.

One official said: “President Hu can't change his tough approach because that was the policy that won him China's top job.”

China may have stopped short of imposing martial law this time, aware as it is of its reputation with only weeks to go before the start of the Beijing Olympics. But the troops are in place. And the crackdown now under way is believed to be no less severe than the measures used to restore order after the previous big riots.

For many, the question is whether the authorities will begin to relax their grip once the Olympics are out of the way.

Many Tibetans in Lhasa say they believe that the police presence will be diminished and security checks will start to disappear once the Olympics have finished. Perhaps the tourists may then start to return and the monks will be allowed into their temple halls and even back on to the streets.

But one Chinese analyst of Tibetan matters expected quite another response by Beijing. “I think that once the Olympics are over we will start to see the real crackdown.

“Now the authorities worry about international opinion, but once the Games are over there will be a settling of accounts. Then we will see many people being sent to jail and even tougher measures to restore order.”