Officials from political parties said on Monday that about 58 students, journalists, human rights workers and politicians were freed on Sunday.
Hundreds of pro-democracy activists, politicians and students were detained by the government during protest rallies or in raids on their homes and offices.
Hundreds more, however, remain in jail throughout the Himalayan nation, many facing long jail terms, they said.
Shobhakar Parajuli, of Nepali Congress, the country's largest political party, said: "Only a few of them were freed in what appears to be an attempt by the government to create confusion."
Call for democracy
Parajuli said as many as 500 of the party's members and supporters remain in jail.
"The more important leaders are still in jail"
Khadga Prasad Oli, deputy leader of the Communist Party
Other political parties also said many of their members were still in detention.
Khadga Prasad Oli, deputy leader of the Communist Party of Nepal, said: "The more important leaders are still in jail."
Oli said the government had released a relatively small number of detainees in an attempt to slow growing anti-king protests.
"We will not slow down our movement. There are still many of us out in the open and we will continue until we restore democracy in Nepal," Oli said.
Legitimising the rule
Since King Gyanendra seized absolute power on 1 February 2005, the main political parties have been organising street protests calling for restoration of democracy.
The parties intensified their protests before last week's municipal elections, which they saw as an attempt by the king to legitimise his rule.
The government also stepped up its crackdown on the opposition, using force to break up protests, jailing activists and imposing a curfew and other restrictions.
Only 21% of eligible voters took part in last Wednesday's elections, in which there were no candidates for more than half of the 4146 available posts.