Thirteen soldiers and one rebel were killed in a gun battle east of the capital Kathmandu on Monday, a day after rebels ended a six-day blockade that had choked supplies and disrupted transport across the nation.
Maoists have stepped up attacks on security bases and on towns and cities since January, when they ended a unilateral ceasefire after the government refused to reciprocate.
More than 13,000 people have died since the conflict began in 1996. The rebels are fighting to topple Nepal's Hindu monarchy led by King Gyanendra and set up a communist republic.
The army said its soldiers had killed at least 20 rebels on Tuesday at Darechowk in Dhading district, a Maoist stronghold 80km west of Kathmandu.
An army officer said: "The operation was launched after a tip-off that the rebels had gathered at a place there."
The army suffered no losses, but police said they had lost 10 of their men in two attacks by the rebels in the east.
In a separate incident, officials said hundreds of Maoists attacked a police post in eastern Nepal and killed nine officers. They said that one rebel also died in the clash.
The Maoists are trying to
overthrow King Gyanendra
A police officer said more than 300 rebels arrived in buses and trucks and attacked the post at Birtamod, a town in a tea-producing region 600km east of the capital.
"At least 20 policemen have been wounded," the officer said.
Bhola Shiwakoti, a senior local government official, said more troops had been rushed to the site. Police said rebels had also shot a police officer in the nearby town of Dharan.