A Sri Lankan army soldier stands guard at a road side checkpoint in Colombo. Photo / Reuters

A Sri Lankan army soldier stands guard at a road side checkpoint in Colombo. Photo / Reuters

Violence has surged since the end of 2005 and the Tigers have reverted to their original demand for independence.

Sri Lanka's 25-year civil war with Tamil Tiger rebels is likely to escalate into the bloodiest period of fighting the island has seen after the Government this week scrapped a tattered truce, experts say.

Sri Lanka plunged back into war after four years of relative peace almost as soon as President Mahinda Rajapaksa took power in late 2005. But both he and the Tigers had held off scrapping a Norwegian-brokered truce to avoid appearing the villain.

With the pact now formally ended, hopes of resurrecting collapsed peace talks any time soon are dead and investment in the US$26 billion ($34 billion) economy could suffer.

"This means all-out war. The Government has dropped the peace option and has opted for a fuller military onslaught on the rebels," said Iqbal Athas, an analyst with Jane's Defence Weekly in Colombo.

Wednesday's announcement came hours after suspected Tiger rebels bombed a military bus in central Colombo, killing four people and wounding 24. It was the latest in a litany of attacks that have killed hundreds in recent months.

Violence continued on Thursday. The military said it destroyed six rebel bunkers in the northwestern district of Mannar, killing six Tigers, while the pro-rebel website, www.tamilnet.com, said the insurgents had thwarted a major Army offensive and killed 10 soldiers. Separately, two soldiers were killed in a mine blast in the northern district of Polonnaruwa.

More than 5000 people have been killed since early 2006, taking the death toll since the war erupted in 1983 to around 70,000.

The Government said the Cabinet decided to scrap the 2002 ceasefire because the Tigers were using it as cover to regroup and rearm and had violated its terms thousands of times.

However, it insisted the door remained open to talks in future if conditions allowed or if the Tigers laid down their arms.

In Washington, US State Department spokesman Sean McCormack said the United States was troubled by a decision he said would "make it more difficult to achieve a lasting, peaceful solution to Sri Lanka's conflict".

"We call on both the Government and the Liberation Tigers of Tamil Eelam to avoid an escalation of hostilities and further civilian casualties," he said.