COLOMBO: Sri Lanka pressed ahead with its battle to destroy the Tamil Tiger rebels Thursday despite international appeals for the two sides to end their civil war and let thousands of civilians trapped in the war zone escape to safety.

The government has vowed to end the 25-year-old civil war and has cornered the separatist rebels in a tiny strip of coastal land. Recent fighting in the area has killed hundreds of civilians.

Media Minister Lakshman Abeywardena said the military was continuing its offensive. "There is no change in the government stance, despite pressure coming from several countries," he said.

With the death toll from the fighting mounting, President Barack Obama on Wednesday demanded the rebels lay down their arms and release the estimated 50,000 civilians they have been accused of holding as human shields. He also admonished the government to stop firing artillery into the war zone.

"Now's the time, I believe, to put aside some of the political issues that are involved and to put the lives of the men and women and children who are innocently caught in the crossfire, to put them first," Obama said in Washington.

His comments came hours after artillery shells slammed into a makeshift hospital in the war zone, killing at least 50 people, setting an ambulance ablaze and forcing the medical staff to huddle in bunkers for safety, doctors said. It was the third deadly attack on the hospital this month.

Both sides welcomed Obama's appeal for an end to the civil war, but ignored his criticism of their conduct.

Sri Lankan Foreign Secretary Palitha Kohona said the government was "extremely reassured" by Obama's call for the rebels to lay down their weapons and release the civilians.

He denied the government was firing artillery into the densely packed war zone, but the U.S.-based group Human Rights Watch says satellite images and witness testimony contradict that claim.

Reports of the fighting are difficult to verify because the government has barred most journalists and aid workers from the war zone.

The rebels' political chief, Balasingham Nadesan, praised Obama in a statement e-mailed to The Associated Press "for passionately talking about the plight of Tamil civilians and calling for urgent actions to alleviate the mounting humanitarian crisis."

The rebels did not address his call for their surrender.

The U.N. Security Council issued similar demands to both sides and expressed grave concern at the worsening humanitarian crisis, but the warring parties showed no sign of backing away from the fight.

Military spokesman Brig. Udaya Nanayakkara said Thursday the army had pushed ahead with its offensive and recovered the bodies of 19 insurgents Wednesday.

He said 1,000 civilians fled the war zone Thursday as the rebels shot at them — injuring several — to try to make them turn back. Nearly 200,000 civilians who already escaped the fighting are in displacement camps in the north.

A wave of artillery bombardments has pummeled the war zone since the weekend, health workers said. Weekend attacks alone may have killed as many as 1,000 people, doctors said.