Sri Lankan military on Monday resumed shelling Liberation Tigers of Tamil Eelam positions in the island's embattled northeast.

The move comes a day after the rebels warned that such strikes could lead to a full-scale war and offered to lift the water blockade.

Military spokesman Upali Rajapakse said troops were keeping up their offensive -- code-named Watershed -- to open a rebel blockade of an irrigation canal in the district of Trincomalee.

"The operation is underway. There is shelling as and when ground troops request it to move in that area," he said.

The rebel Liberation Tigers of Tamil Eelam said 15 more civilians were killed in the latest artillery attacks carried out by the military.

'The government action by implication not only rejected LTTE's goodwill gesture but also shows that the government is paying scant regard to Norway's peace efforts,' the LTTE said.

'The very next day, at 7.30 am on the morning of 7 August, 15 civilians were killed when government forces shelled the civilian areas in the LTTE administered section of Muttur,' the Tigers' statement said.

The fighting since last Wednesday at Muttur, which the military said was a diversion from the main battles near the Maavilaru min-dam, or anicut, has left some 30,000 refugees.

Concern also mounted for the safety of local and foreign relief workers after the news that 15 people working for the French humanitarian agency, Action Against Hunger were killed in Muttur on Friday.

Security forces and Tigers blamed each other for the killing.