The Tamil Tigers have accused the Sri Lankan government of shelling civilians and wreaking carnage during its military offensive in the north.
The government has denied the allegations, in turn accusing the rebel group of targeting civilians.
The army has said at least 25,000 civilians have fled the Tamil Tiger-held area.
The rebels have so far rejected government calls to surrender, or face a final assault.
The rebel spokesperson, Thileepan, said a hospital, an orphanage and many houses had been hit and huge numbers of civilians had been killed in a military onslaught of the area.
He said people had been reduced to hiding under logs and trees and using makeshift bunkers dug into the sand.
The Sri Lankan military has denied shelling civilians inside the rebel-held area.
Army spokesman Brigadier Udaya Nanayakkara told the BBC that only small-arms had been used.
He said the Tigers were targeting civilians because they knew that if non-combatants left, the rebels would be "sitting ducks".
The army says three rebel suicide bombings had targeted fleeing civilians, killing 17.