Nepalese police arrested 18 people in Kathmandu on suspicion of "anti-China activities" yesterday, the 54th anniversary of the 1959 rebellion against Chinese sovereignty over Tibet.
All but three were released from custody within hours, police said.
Nepal, home to around 20,000 Tibetans, is under intense pressure from Beijing over the exiles, and has repeatedly said it would not tolerate what it calls "anti-China activities".
On February 13 a Tibetan monk doused himself in petrol in a Kathmandu restaurant and set himself on fire, in the 100th self-immolation by a Tibetan since 2009 in a wave of protest against Chinese rule.
The gruesome burnings, most of which have occurred in Tibetan-inhabited areas of China, are seen as a sign of desperation in the community over perceived religious and political persecution in Chinese-ruled Tibet.
The Nepalese government had stepped up security efforts ahead of the anniversary. Home ministry spokesman Shanker Koirala was quoted as saying last week the government was making "security arrangements … to foil any untoward incidents".