A suspected Tamil Tiger suicide bomber killed Sri Lanka's highways minister and at least 11 others on Sunday gathered for a marathon race near the capital, the government said.

"Minister Jeyaraj Fernandopulle is dead from the explosion," Laksman Hulugalla, director general of the media centre for national security, told Reuters.

A former top Sri Lankan marathon runner, K.A Karunarathne, was among those killed while 100 people, some of them participants in the race to mark the upcoming New Year, were wounded.

The attack comes amidst an offensive launched by the Sri Lankan military on the northern strongholds of the Liberation Tigers of Tamil Eelam (LTTE) in which at least 100 rebel fighters were killed last week, the military said.

The rebels have in the past hit back with bombings in the capital, Colombo, and in the relatively peaceful south of the war-ravaged island when they have come under military pressure in the north and east.

Sunday's attack took place in the town of Weliveriya, 30 km (19 miles) from Colombo, where Fernandopulle had gone to flag off the marathon race.

Television footage showed a ball of fire moving towards the minister as he signalled the start of the run.

"Its a suicide attack, definitely by the LTTE," said a bomb squad official, speaking on condition of anonymity from the scene.

President Mahinda Rajapaksa condemned the killing, blaming it on the LTTE, but said it would not weaken his government's resolve to put down terrorism.

"The assassination of such a committed democrat once again shows the total contempt of the LTTE to the democratic process, and its unquestioned commitment to violence and terror to achieve it narrow and limited objectives, that are far removed from the interests of the Tamil people of Sri Lanka," he said in a statement.

"While calling on the people to be calm and collected in the face of such extreme provocation by the forces of terror, I wish to reiterate that this dastardly act will not weaken our resolve to eradicate terrorism from our midst.

The LTTE, which usually denies any involvement in such attacks, was not immediately available for comment.

SECOND KILLING

Fernandopulle, 55, was a member of the government negotiating team for failed peace talks with the Tamil Tiger rebels two years ago.

He was the second minister to be killed since January, when the minister for nation building, D.M. Dassanayake, died in a roadside blast in the same district, Gampaha.

Foreign minister Lakshman Kadirgamar was the most senior government leader to be killed in recent years, shot dead at his home in Colombo by a suspected Tamil Tiger sniper in August 2005.

The Tigers are fighting for an independent state in the north and east of the island in a 25-year civil war that has killed an estimated 70,000 people.

In January the government called off a tattered 2002 ceasefire, accusing the rebels of using it to regroup and re-arm, and vowed to fight them militarily.

Analysts say the military has the upper hand in the latest phase of the long-running war given superior air power, strength of numbers and swathes of terrain captured in the island's east. But they still see no clear winner on the horizon.