Nepal's military officials say at least 36 people were killed when a landmine exploded under a crowded bus on a rural road south of Kathmandu early Monday.
They say more than 70 people were wounded, some critically.
The officials say they suspect Maoist rebels carried out the attack, which is described as one of the worst against civilians since the insurgency began in 1996.
Army officials say the attack took place in Chitwan district, a known rebel stronghold about 150 kilometers south of the capital.
Maoist guerrillas have stepped up violence since February 1, when King Gyanendra dissolved parliament and assumed absolute power.
The king says the move was necessary to quell the insurgency that has already claimed about 12,000 lives.
Some information for this report provided by AP, AFP and Reuters.
