Seevarathnam Puleedevan, a senior leader of the Liberation Tigers of Tamil Eelam (LTTE), said Sri Lankan warplanes had bombed a Tiger base in the east of the country inflicting heavy casualties on Friday.
He also said civilians could not move because of the presence of the Sri Lankan forces and asked Norway to help the 42,000 civilians trapped by the fighting, who are suffering shortages of food and essentials.
"We have urged Norway to address the humanitarian needs of the civilians trapped here ... it is getting serious," he said.
Fighting for waterway
The appeal came on the second day of fighting in the northeast, where the military is trying to secure a waterway after a dispute with the rebels triggered some of the worst clashes since the two sides signed a Norwegian-brokered ceasefire in 2002.
Thursday's clashes left 61 combatants dead, according to the two sides.
Tom Knappskog, the Norwegian embassy spokesman, declined to comment on the specific request, but said: "We are in close contact with both the government and the LTTE as we have been all along."
The Sri Lankan government's spokesman was not immediately available for comment, but Major Upali Rajapakse, a military spokesman, said the intensity of fighting on Friday was lower compared to the day before.
There were no known casualties on the military side on Friday, he said.
Rajapakse said the military was defending its position near the reservoir and the waterway.
"Our operation will continue until we fully secure the whole area," he said.
The Tamil Tigers began fighting in 1983 for a separate homeland for the country's 3.2 million Tamils, saying the ethnic minority can only prosper away from the domination of the 14 million Sinhalese majority.
The ceasefire put a temporary halt to the bloodshed, but the truce has nearly collapsed with almost daily violence in recent months.