A bomb has exploded on a bus in Sri Lanka's second city, Kandy, killing one person and injuring twenty others.

The bomb exploded as passengers were boarding it at the city's bus station. The bus was headed for the northeastern town of Polonnaruwa.

It's not known who was responsible for the blast but the BBC correspondent in Colombo says it will be blamed on the rebel Tamil Tigers who are fighting for a separate homeland for the minority Tamil population.

It was the third fatal explosion in just two months. In January last year, Tamil Tiger suicide bombers exploded a truck outside Sri Lanka's holiest Buddhist site, the Temple of the Tooth , in Kandy.