Krishna Pahadi, the founder of the Human Rights and Peace Society, says Nepalis are ready to fight back against King Gyanendra's takeover of the government last week.
"We would like to fill the jails of Nepal for the sake of democracy, human rights and the peace," he said.
Mr. Pahadi's group, along with other human rights groups, teachers and Nepalese journalist associations say they will hold a demonstration in the capital Kathmandu on Thursday. It promises to be the most visible public reaction to the takeover so far.
The announcement comes as the king and his hand-picked government continue to tighten controls over Nepalese society. On Monday, Nepal's new royal government banned criticism of the security forces, and warned that violators could be put under house arrest.
The government also banned political activity by public servants, and said the authorities could seize private property if necessary.
Mr. Pahadi says he is aware that by announcing plans for the demonstration, activists could be opening themselves up to arrest or possible violence at the hands of the security forces. But he says that does not matter.
"They try to intimidate anyway, but this is our duty. We would like to fight non-violently for fundamental freedom and human rights, continuously," he said.
King Gyanendra's takeover included placing rights workers, journalists and political leaders under house arrest, largely shutting down communications between Nepal and the outside world, and deploying troops in the streets of the capital.
The crackdown so far appears to have stifled dissent. Unlike other times of political turmoil, no large-scale anti-government demonstrations have yet taken place.
The king says he acted for the good of the nation, because the political parties failed to organize elections, or to end a long-running insurgency carried out against the government by Maoist rebels.
The rebels have been waging a violent campaign to topple the monarchy for the past nine years. On Thursday, state media reported that the king has appointed special representatives to hold peace talks with the rebels. But he has also warned that if the peace talks fail, the rebels could face a new military offensive.