At least 37 rebels and three policemen have been killed in Nepal as violence resumed at the end of a temporary cease-fire declared by the Maoists.

Officials say that under the cover of darkness, hundreds of rebels attacked a police post at Khas-Kusum village, about 450 kilometers west of the capital, Kathmandu.

Several policemen were killed or injured in the clash, which continued until dawn Saturday.

Police reinforcements were rushed to the area and troops are searching for the rebels, who fled into nearby jungles. Officials say they have recovered the bodies of many guerrillas killed in the clash, but independent confirmation of casualties is difficult due to the remote location of the clashes.

The area lies in the midst of a Maoist stronghold. Rebels control about one-fourth of the countryside in Nepal.

The rebels sprang the attack at the same time a temporary truce expired on Friday. The rebels called the nine-day cease-fire to mark the kingdom's Hindu Dashain festival, the biggest of the year.

Officials say the latest clash is one of the worse since rebels pulled out of peace talks in August, ending seven months of peace. Since then, nearly 400 people have been killed in fighting between security forces and the rebels.

Maoist guerrillas began their struggle to set up a communist republic in Nepal in 1996. So far two attempts at negotiating peace with the rebels have collapsed - in 2001 and in August of this year.

The rebels want to abolish the country's constitutional monarchy. They are asking the government to establish an assembly that will draft a new constitution, but the government says it can only make amendments and will not concede to changes in its existing multi-party democracy.

The rebellion has become more violent in recent years - more than half of the eight thousand people killed in the eight-year conflict died last year. The conflict has raised worries about the future of democracy in one of the world's poorest countries.