Colombo, Sri Lanka ? Sri Lankan forces shelled a makeshift hospital in the war zone Saturday, killing 64 civilians despite a pledge to stop using heavy weapons in its battle with the Tamil Tigers, a rebel-linked Web site said.

A health official in the war zone confirmed the hospital was hit twice by artillery throughout the day, though the official declined to say who was responsible. The military denied launching the attack.

Sri Lanka has come under increasing international pressure to halt its offensive against the rebels to safeguard the estimated 50,000 ethnic Tamil civilians trapped by the fighting.

The government, which has cornered the Tamil Tigers in a 3-mile-long coastal strip, has refused, but it did promise to stop launching artillery and airstrikes into the area.

The TamilNet Web site said the government hit the makeshift hospital at Mullivaaykkaal twice on Saturday morning.

The attacks killed at least 64 patients and bystanders and wounded another 87, according to a government health official. The official, who said he was not certain of the source of the attack, declined to be identified because he was not authorized to speak to the media.

The attack killed a female volunteer doctor and wounded three medical workers, the Web site said.

Though the hospital is inside rebel-held territory, it is run by government doctors.

The government denied the army had shelled the war zone, saying soldiers were only using small arms in the fight to destroy the rebels.

“There is absolutely no truth in these reports,” Foreign Minister Rohitha Bogollagama said.

Bogollagama spoke after meeting with Japanese peace envoy Yasushi Akashi, the latest high-profile diplomat to arrive in Sri Lanka in the past week.

Akashi met with President Mahinda Rajapaksa during his visit and also traveled to displacement camps where more than 100,000 civilians who fled the war zone in recent weeks have been held.