Colombo: An explosion hit a bus in Sri Lanka on Friday, killing two people just hours after suspected rebels carried out an attack that left at least 21 others dead.

Police said two people were killed and 20 others injured in the latest explosion that took place near a teacher training school in Kandy.

Earlier on Friday, a bomb targeted another bus in Colombo, killing 21 civilians and injuring at least 47 others, the Defense Ministry said.

A curfew has been imposed in the area to give soldiers and police a chance to search for suspected rebels.

The military blamed the attack on the Liberation Tigers of Tamil Eelam, saying the rebels used a remote-controlled bomb to hit the bus near a Buddhist temple in Moratuwa.

President Mahinda Rajapaksa called on Sri Lankans to "remain vigilant against the forces of terror," after Friday's first attack.