"More than 1,350 people have been arrested since 19 January for either organising or participating in political demonstrations," said an Amnesty statement.

"Of those, at least 888 are believed to still be detained."

Nepal's home ministry disputed the figures but did not provide details. "All the political detainees will be released gradually," said spokesman Gopendra Pandey.

About 50 people, including 30 journalists, were detained in protests in Kathmandu on Wednesday but a mass demonstration against the king's rule fell flat after police moved in to prevent crowds gathering.

The journalists were released later Wednesday but many political leaders remain under house arrest, local rights activists say.

"You did not see a mass mobilization because the senior leaders who could mobilise people are in jail and have been for the last 10 to 12 days," said Kanak Mani Dixit, editor of Himal South Asia magazine, who was held briefly on Wednesday.