"It is a suicide blast on Platform 3. The bomber has got down from a train and exploded," military spokesman Brig. Udaya Nanayakkara said, blaming separatist Tamil Tiger rebels.

"The target appears to be civilians," Nanayakkara said.

Telephone calls to rebel spokesman Rasiah Ilanthirayan's office were not answered Sunday.

Anil Jasinghe, a doctor at Colombo National Hospital, said at least eight people were killed in the blast and 100 more were wounded, 10 of them badly.

"I was near my counter and I heard a big blast. When I looked behind I saw a policeman bleeding," said Ravindra Pinto, a ticket inspector at the station.

"As I took him and rushed out, I saw many men and women on the ground," said Pinto, who was not injured in the blast.

The explosion comes a day after a bomb on a bus killed 18 people, mostly Buddhist pilgrims, in the central town of Dambulla, about 150 kilometers (90 miles) northeast of Colombo.

Earlier Sunday a grenade exploded at a zoo on the outskirts of Colombo, wounding at least four people.

Tamil rebel suicide bombers, known as Black Tigers, have undertaken more than 240 suicide attacks in the separatist group's near-25-year campaign. The United States, European Union and India all list the Liberation Tigers of Tamil Eelam — as the insurgents are officially known — as a terror group.

The rebels have been fighting since 1983 for an independent homeland for Sri Lanka's ethnic minority Tamils after decades of being marginalized by Sinhalese-dominated governments. The fighting has killed more than 70,000 people.

More than 700 people have been killed in intensified violence since the government withdrew from a cease-fire with the separatist Tamil guerrillas last month. Civilians have borne the brunt of the violence.