A veteran political opponent of the Tamil Tigers was injured today and three people were killed when his vehicle was torn apart by a bomb in the Sri Lankan capital of Colombo.

The bomb, the first in Colombo in nearly four months, coincided with the funerals of 17 local tsunami aid staff butchered in north-eastern Sri Lanka last weekend, and brought the death toll from the island’s escalating violence over the past fortnight to 440.

The remote-controlled bomb marked a change in tempo in the fighting which, since it erupted last December, has been confined to the north and east of the country, and raised fears that a tattered three-year-old ceasefire had finally given way to all-out war.

The target was Sankarapillai Sivathasan, an adviser to the Eelam People’s Democratic Party (EPDP) which broke with the Liberation Tigers of Tamil Eelam (LTTE) when it went mainstream in 1987.

The 72-year-old former MP was in stable condition in hospital today, but his bodyguard died in the fireball which engulfed Mr Sivathasan’s white Hyundai minivan outside a girls’ school in a residential area.

The other victims were a three-year-old girl walking with her mother, who was severely injured, and a male passer-by.

As police forensic teams examined the scene hours later, a charred corpse could still be seen in the van’s wreckage, and the badly burnt body of the young girl, Asini Sashida, lay a few yards away.

John Rasah, the child’s 61-year-old grandfather and a Tamil Catholic, motioned to a spilled bag of rice and said his daughter had been carrying it home for dinner. “We are only poor people. I don’t understand all this,” he said through tears.

The only good news for this battered island today came when Jon Hanssen-Bauer, the Norwegian peace envoy struggling to hold together the 2002 ceasefire agreement, convinced the Tigers to reopen a blocked waterway over which the rebels and the Sri Lankan military had been fighting for the past two weeks.

That fighting had centred on the northeastern town of Muttur, causing thousands of residents to flee. It was there that the 17 Sri Lankan employees of Action Contre la Faim (ACF), a Paris-based international relief agency, were found on Sunday, lying face down on a lawn outside their office with bullet wounds to their heads. Two had been shot as they tried to escape in a car.

The rebels and the Government both blamed each other for the execution-style killings, and the Government ordered an investigation.

“[They were] seemingly lined up and shot at very close range. The sight was too much to handle,” a fact-finding mission of the Consortium of Humanitarian Agencies (CHA), an independent monitor, reported.

“ACF’s entire team in Muttur was assassinated,” the charity said. “Now that it is clear this was a mass murder targeting clearly identified humanitarian workers, ACF is determined not to settle for vague answers from the parties to the conflict ... and will demand exemplary punishment.”

The 13 men and four women water sanitation engineers - 16 of whom were Tamils - were buried today by the seafront in the nearby port city of Trincomalee where one woman collapsed, grieving for both her 54-year-old husband and her 27-year-old daughter.

“We believe it was the army,” said Richard Arulrajah, 50, whose 24-year-old son was among the dead. “On Friday he phoned and said he would be back by Saturday. After that, we heard the military personnel came and shot them.”

Aid workers are targeted by Sri Lankan hardliners because they are perceived to harbour pro-Tamil sympathies. Other aid workers have been attacked by Sinhalese mobs in recent days.

Yogaraja, a 62-year-old labourer staring through the mortuary window trying to identify the body of his son Kodeswaran, 31, said: “I don’t know who killed my son. But everyone involved in the fighting should be blamed.”

ACF has now suspended its mission to Sri Lanka where its 15 expatriate and 224 local workers provided humanitarian relief in areas hit by the December 2004 tsumani.

Philippe Douste-Blazy, the French Foreign Minister, condemned “the appalling and cowardly murders”, which represented the worst attack on aid workers since the 2003 bombings of UN’s Baghdad headquarters.

Bill Clinton, the former US President and UN envoy for tsunami recovery, urged the Sri Lankan authorities “to do everything possible to apprehend the perpetrators of this crime and to bring them to justice”.

Despite the Tigers’ agreement to reopen the waterway, which supplies 60,000 people in goverment-controlled villages, the Government said it had not been involved in the talks and continued to fire artillery.

Major General Ulf Henricsson and Ove Jansen, from the Sri Lanka Monitoring Mission, narrowly escaped the shelling, according to TamilNet, a pro-Tamil website.

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