A female suicide bomber attacked the main railway station in the Sri Lankan capital Sunday, killing at least 11 people and wounding 92 others, officials said.

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Military spokesman Brig. Udaya Nanayakkara said the bomber got down from a train and then blew herself up.

"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 wounded in the blast.

Nanayakkara said 11 people were killed and 92 others wounded in the attack, which he blamed on the separatist Tamil Tiger rebels.

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

The attacks took place as the government prepared to hold celebrations across much of the country to mark the 60th anniversary of Sri Lanka's independence from Britain on Monday. The usually tight security across the capital was further heightened in recent days as troops searched cars and pedestrians ahead of a national ceremony on the city's major coastal road.

"There are tight security programs being imposed," Nanayakkara said, but the security forces had difficulty stopping suicide attackers.

On Saturday, a bomb on a bus killed 18 people, mostly Buddhist pilgrims, in the central town of Dambulla, about 90 miles northeast of Colombo.

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.

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.