The victim, a member of an intelligence unit, was taken off of a bus and killed in broad daylight near the town of Batticaloa, the official said.

The killing came on the eve of a visit to Sri Lanka by Norway's Foreign Minister Jan Petersen in a bid to jumpstart peace talks to end the three-decade ethnic conflict.

The Tamil Tigers said a ceasefire brokered by Norway in place since February 2002 was at risk because government troops were behind the killing Thursday of two rebels in Batticaloa, 300km east of Colombo.

The military has denied the charge.

"It is apparent that the killers have all the assistance from the SLA (Sri Lankan army)," the Tigers' political wing leader S.P. Thamilselvan said in a letter to Scandinavian truce monitors.

"We request you to advise the government that if the SLA continues to act in this manner the entire peace process and the ceasefire agreement are being placed in heavy risk and dire consequence have to be faced," he said.

"We are afraid that it may become impossible for us to be patient onlookers of this cavalier fashion in which killing are being carried out."

Thamilselvan asked Trond Furuhovde, a retired Norwegian army general who heads the ceasefire monitors, to investigate the two killings and take action.

Local officials said Thursday's killings appeared to have been a retaliatory attack for the slaying of another rebel who was from the remnants of a renegade faction crushed by the Tiger leadership last month.

Diplomats said the killings are likely to figure in to the Norwegians' talks this week to revive peace negotiations which have been on hold since April last year.

The Norwegian foreign minister is due in Sri Lanka Monday and has a meeting schedule with the elusive Tiger Tamil chief Velupillai Prabhakaran.

The LTTE brought its London-based chief negotiator Anton Balasingham, 65, to the rebel-held Wanni region Friday ahead of the hectic shuttle diplomacy expected in coming weeks.

Diplomats said Petersen's visit will be followed by one from Japan's special peace envoy to Sri Lanka Yasushi Akashi, who last June helped boost peace prospects by raising 4.5 billion dollars in aid pledges to rebuild Sri Lanka.

"There is a concern that a lack of progress in Sri Lanka will force donors to turn their attention to other troublespots needing help," a diplomatic source close to the peace process said.

"It's difficult for Norway to keep Sri Lanka in the international agenda unless the parties make progress," the source said. "The huge support last year was due to the feeling peace was possible in Sri Lanka."