Nepal police on Tuesday detained more than 100 Tibetan refugees who had gathered to celebrate the Dalai Lama's 75th birthday, but released them later in the day.

The government has banned Tibetans from marking their exiled spiritual leader's birthday in public places as Nepal recognises Tibet as an integral part of China.

"Those detained were released following interrogation," said Kathmandu district police chief Ramesh Kharel. "They may observe celebrations in monasteries," he added.

Police prevented Tibetans from heading towards the celebration venue at the Jawalakhel grounds in Kathmandu from different parts of the city.

Tsering Lama, a member of the Students for Free Tibet group, said it took three hours to reach the celebrations. "We had to keep finding new ways of getting here and dodging the police."

Some Tibetans had been out since early in the morning, waiting for the celebrations to begin. Old men and women braved the rain to walk to the venue.

"I am very angry because I can't attend the celebration. I was turned away by the police," said Yeshi Wangmo, a Kathmandu-born Tibetan exile.

Monks and nuns were also prevented from leaving their monasteries in Kathmandu.

The government issued a directive to members of the Constituent Assembly, asking them not to participate in birthday celebrations, the Himalayan Times reported.

The Foreign Ministry also called on all parties to make sure none of their members participated.

Nepal stepped up security in the capital, as well as on the northern border adjoining Tibet.

Officially some 20,000 Tibetan refugees live in Nepal.