It was the largest number of Tibetans detained in a single day in the capital since the exiles began almost daily protests last month against a Chinese crackdown on riots in Tibet.
Police in camouflage uniforms chased down red-robed Buddhist monks and nuns and other Tibetans, dragging some along the ground by their feet or hands as they resisted. Many were shoved into waiting vans and trucks.
Even as the vehicles hauled them away to detention centers, some held banners that read "Free Tibet" or shouted "Stop killing in Tibet."
No injuries were reported except for minor cuts and bruises on both sides, police said.
A total of 505 Tibetans were detained in at least three separate demonstrations near the Chinese Embassy in an upscale Katmandu neighborhood, said police official Sarbendra Khanal.
Before the protests began, police had already detained a number of Tibetans who were preparing to demonstrate, Khanal said.
The Tibetans detained Thursday had not been charged and authorities were awaiting top government officials' orders on handling them, Khanal said. Most detained in previous protests were freed the same day, but Khanal said he did not know when the latest group would be released.
In neighboring India, runners carried the Olympic torch along a heavily guarded route through central New Delhi. It was protected by about 15,000 police who kept away Tibetan exiles and other anti-China protesters in some of the tightest security ever seen in the Indian capital.
Nepalese police have broken up almost all the anti-China protests of the past few weeks and detained numerous demonstrators. Officials have said they will not allow protests against any friendly nations, including neighboring China.
Security has been tightened around the Chinese Embassy since the protests began. Hundreds of police officers have been guarding the streets leading to the building.
The protesters have so far gathered in small groups near the embassy, but have not been able to enter the fortified compound.
The U.N. and international rights groups have accused Nepal of using excessive force against the Tibetan demonstrators. Police have broken up protests by beating people with batons and dragging them through the streets. This week, police had initially appeared to be using less force.