According to China's official news agency Xinhua, Nepal Police had to step in and disperse the rally, when the demonstrators shouted anti-China slogans and reiterated demands for a free and independent Tibet. During the ensuing melee, some Tibetan leaders of the rally climbed the wall of a nearby cinema, and instigated others to ignore the police's attempts at dissuasion.
Xinhua quoted the Kathmandu Police Control Center as saying that the detainees were supposed to be released after being questioned in various police stations.
The Government of Nepal has repeatedly said that Tibet is an inalienable part of China, and that it will not allow any anti-China activities on its territory.
Tibetan separatists have staged frequent anti-China protests in Kathmandu since mid-March. The activities often turned ugly, leading to disruptions of city traffic and clashes with police which injured Nepali policemen.
Chinese Ambassador Zheng Xianglin said last month that there were criminal acts of beating and smashing by Tibetan separatists in Kathmandu against other Tibetans who either refused to take part in anti-China activities or held different positions from the separatists.