COLOMBO, Sri Lanka - A suicide bomber attacked the opening ceremony of a marathon outside Sri Lanka's capital Sunday, killing a government minister and 11 other people, authorities said. Dozens were wounded.

Officials blamed the bombing, the second this year resulting in the death of a senior government official, on Tamil Tiger rebels.

Runners and onlookers gathered at the starting line of the marathon in Weliweriya, 19 kilometres from Colombo, part of the national celebration of the upcoming Sinhalese New Year.

Jeyaraj Fernandopulle, the minister of highways and the ruling party's chief whip, approached the starting line with a flag he planned to wave to start the race when the bomb exploded, witnesses said.

"There was a sound of huge explosion and I saw a fireball" said Nishan Priyantha, a local journalist who stood few yards away from the blast, but escaped unhurt.

Television footage showed chaotic images of screaming people running through the bloodied streets.

Fernandopulle, an acid-tongued politician who acted as the government's chief political enforcer and was considered a top rebel target, died on the spot, said government spokesman Lakshman Hulugalle, blaming the rebels.

"I saw the minister's body. It had been torn into pieces below the waist and there were other bodies without heads and legs," Priyantha said.

Eleven others were killed -- including 1992 Olympic marathoner K.A. Karunaratne and national athletic coach Lakshman de Alwis -- and more than 90 were wounded, Hulugalla said.

President Mahinda Rajapaksa condemned the attack as an act of savagery and vowed to push ahead with the war on the rebels.

"This dastardly act will not weaken our resolve to eradicate terrorism from our midst, and bring peace, harmony and democracy to all our people," he said in a statement.

Rebel spokesman Rasiah Ilanthirayan did not answer calls seeking comment. The Tamil Tigers, listed as a terror group by the United States and European Union, routinely deny responsibility for such attacks.

Fighting in Sri Lanka has increased in recent months since the government officially ended a six-year cease-fire in January. The truce had been faltering for more than two years as escalating violence killed about 5,000 people.

The military has vowed to crush the rebels by the end of the year, but diplomats and other observers say the army is facing more resistance than it expected.

The Tamil Tigers have fought since 1983 for an independent homeland for ethnic minority Tamils, marginalized for decades by successive governments run by majority ethnic Sinhalese. More than 70,000 people have been killed in the violence.

Fernandopulle was the fourth Sri Lankan lawmaker to be killed this year. In January, Nation Building Minister D.M. Dassanayake was killed in a roadside bomb attack blamed on Tamil rebels.

One opposition lawmaker was gunned down in Colombo and another died in a bomb explosion in the rebel-held northern region.