Security forces killed at least 350 guerrillas in gunbattles in western Nepal, the Defense Ministry said Saturday, in what would be the deadliest spate of fighting in the rebels' 6-year-old campaign to oust the constitutional monarchy.

The attack by security forces on rebel camps and hide-outs in Lisne, a village and guerrilla stronghold some 220 miles west of Katmandu, began Thursday and lasted until Friday night, the ministry said in a statement.

The death toll could not be confirmed independently. The rebels do not comment on such incidents.

The statement said several guerillas were also arrested during the army offensive, which came after the Maoists attacked a team of security forces patrolling the area.

The bloodshed comes ahead of comes ahead of Prime Minister Sher Bahadur Deuba's visit to Washington next week. He is scheduled to meet with President Bush to discuss the insurgency.

The Bush administration recently asked Congress for $20 million in military aid for Nepal.

Human rights group Amnesty International has accused both the security forces and the insurgents of killing civilians and committing other atrocities.

On Friday, the defense ministry said it had killed 40 guerillas in the gunbattles. The death toll increased to 350 as security forces searched for more hide-outs and killed more guerrillas, including several local commanders, the ministry's statement said Saturday.

The rebels, who operate in more than half of this mountainous Himalayan kingdom of exquisite beauty, are demanding sweeping land reforms and an end to the constitutional monarchy. Their insurgency, inspired by Chinese communist leader Mao Tse-tung, has claimed more than 3,000 lives since it began in 1996.

Until the latest battles, the highest previous death toll was on April 11-12, when more than 200 policemen and guerrillas were killed.

The government intensified its campaign against the rebels after the guerrillas called for a nationwide strike last week that did not get much public support.

On Friday, Deuba rejected a reported offer by rebel leader Prachand to hold peace talks. Nepali newspapers on Thursday said they had received a statement from Prachand, whose real name is Pushpa Kamal Dahal, offering to resume talks that ended in a stalemate last year.

"There is no possibility of talks with the guerrillas until they surrender weapons to the security forces," Deuba said.

King Gyanendra imposed a state of emergency Nov. 26 and ordered the army to clamp down on the rebels after they withdrew from peace talks and attacked government troops and offices.

The rebels are active in 29 of Nepal's 75 districts. Rolpa district, this week's battle ground, is considered a Maoist stronghold.

On Friday, the defense ministry said it had killed 40 guerillas in the gun battle. The death toll increased to 350 as security forces searched for more hide-outs and killed more guerrillas, including several local commanders, the ministry's statement said Saturday.