At least 45 civilians were killed and 125 injured yesterday in heavy shelling by government forces in eastern Sri Lanka, a Tamil Tiger spokesman said.
"We fear the casualties could be higher," Liberation Tigers of Tamil Eelam (LTTE) spokesman S. Puleedevan said.
Sri Lankan military spokesman Prasad Samarasinghe said he was not aware of civilian casualties but confirmed "heavy artillery and mortar bomb exchanges" in Batticaloa district, 250km northeast of the capital.
The shelling came as security forces and Tamil Tiger rebels accused each other of trying to spark full-scale war.
Nearly 3,300 people have been killed in fighting in the past year despite a 2002 truce in Sri Lanka's separatist conflict.
On Tuesday, the LTTE and the military both claimed several civilians and combatants had been killed or injured since Sunday in artillery duels in the east and north of the island.
The military has also accused the LTTE of using civilians as a shield to attack government forces by mortar in the restive eastern region. Samarasinghe said five soldiers were wounded in LTTE shelling late on Monday.
Tiger military spokesman Rasiah Ilanthiriyan on Monday denied the military claim and said they fired mortars in self defense.
Sri Lanka's key foreign aid donors -- the US, EU, Japan and Norway -- have asked the government and the Tigers to refrain from military action after peace talks between the combatants collapsed in Geneva last month.
The collapse left tens of thousands of residents of northern Jaffna Peninsula cut off from food and other essentials as government troops blocked the main highway to the area because rebels use it to transport supplies.
Human rights abuses have been on the rise in the region with the UN this week calling for an investigation into hundreds of deaths since December in addition to a probe ordered by the Sri Lankan government.
"Any commission of inquiry can only investigate a selection of cases, and a broader international mechanism is still needed to monitor, ultimately prevent, human rights violations in the longer term," UN High Commissioner for Human Rights Louise Arbour said in a statement.