Tibetan exiles in Kathmandu are facing increased pressure from Nepal's authorities for their determined protests against China's control of Tibet.
Human Rights Watch says police are pre-emptively detaining monks and other Tibetans as they try to move around Kathmandu, even when they are not engaged in protest.
Some of those detained have been threatened with deportation, in what Human Rights Watch describes as an effort to silence peaceful dissent.
A Tibetan activist, who wanted to be identified only as 'Dorje' described the threats made by Nepalese police.
"They were saying that they will take everybody inside the truck and then they will reach to the border of Tibet and they will hand over all the people to the Chinese soldiers," said Dorje.
Dorje said police have been posted around Kathmandu's main Tibetan stupa in Bouddha, as well as surrounding a refugee camp and a nunnery.
"They are stopping the Tibetan people, especially the monks, they are stopping them from going outside of Bouddha to the town and they are singling out Tibetans and taking them out of the vehicles and taking them to the jail and the prison," he said.
For the past two weeks Tibetan exiles have tried almost every day to hold peaceful protests in front of the U.N. headquarters in Kathmandu and near the Chinese embassy.
Nepalese riot police have dispersed the rallies with baton charges and the temporarily detention of hundreds of Tibetans.
Nepal officially supports Beijing's 'One China' policy, considering Tibet and Taiwan part of China, and the Home Ministry has said it will not tolerate protests against what it describes as "friendly countries".
Human Rights Watch has called for Nepal to end the arbitrary detentions, threats, and harassment of Tibetans in Kathmandu, and condemned the excessive force used by police.