An army officer said on Sunday that the bodies of the 17 Maoists and some of their weapons had been recovered from a village in Makawanpur district, 100km east of the capital Kathmandu, the site of clashes on Saturday night.
He said: "We suffered six casualties."
Another officer said clashes had also taken place in Syangja in western Nepal but gave no details.
The latest violence comes a week after the guerrillas carried out co-ordinated attacks around the capital, killing 12 policemen.
At least 73 people have been killed in insurgency-related violence since the Maoists, fighting a 10-year revolt to overthrow the monarchy, ended a unilateral ceasefire on 2 January after King Gyanendra's government failed to respond.
The Maoists made no immediate comment on the latest clash.
Also on Sunday, a candidate in next month's municipal elections in southern Nepal was killed.
Bijaya Lal Das was shot near his office at Janakpur, about 300km southeast of the capital, Kathmandu, a local government official said on condition of anonymity due to security fears.
Anti-royal demonstrators were
arrested after the protests
Das was a local leader of the Nepal Sadbhawana Party, which supports King Gyanendra.
He was a candidate for mayor of Janakpur in nationwide municipal elections on 8 February.
The rebels have made no comment on the attack but have said they will take action against those who announce their candidacy or help the government to hold the elections.
Das is believed to be the first candidate to be killed by the rebels.
On Saturday police arrested 236 activists after anti-royal demonstrators in Kathmandu clashed with officers who used tear gas and carried firearms in place of their usual bamboo batons.
On Sunday police said most of the detainees had been freed.
Opposition politicians said they would keep up the protest programme, calling a nationwide general strike for Thursday and planning district-level protests in an attempt to disrupt municipal elections.
"The people's movement has come to a new height and will not come to an end unless full democracy is restored"
secretary of the Nepali Congress Party
Shobhakar Parajuli, secretary of the Nepali Congress Party (NCP), told AFP: "The people's movement has come to a new height and will not come to an end unless full democracy is restored."
The parties have vowed to boycott the polls, saying a free and fair vote was impossible under the royalist regime.
Minendra Rijal, spokesman for the NCP, said: "We'll continue to protest until democracy is restored."
Gyanendra seized absolute power last February, sacking a multi-party government and suspending civil liberties.