At least 52 civilians in northern Sri Lanka have died because of fighting in the last 24 hours, while cluster bombs have led to the closure of the area's last functioning hospital, officials said Wednesday.

This undated picture provided by independent observers in Sri Lanka on Wednesday shows a Sri Lankan ethnic Tamil girl lying on a bed at a hospital in Puthukkudiyiruppu, about 275 kilometres north of Colombo, Sri Lanka. (Associated Press)

The hospital in Puthukkudiyiruppu, which was the last medical facility in the war zone, is now closed after enduring days of artillery attacks, officials said.

The Red Cross evacuated the staff and remaining 300 patients on Wednesday and aid workers were trying to find them a better place to stay or get the two sides to grant them safe passage out of the conflict zone, said Sarasi Wijeratne, spokeswoman for the International Committee of the Red Cross.

It's unclear whether government forces or guerrilla group the Liberation Tamil Tigers of Eelam were responsible for the attacks on the hospital.

The military has denied involvement in the attacks on the hospital, the BBC reported, while there has been no comment from the rebel Tamil Tigers.

The reported cluster bomb attacks mark the first usage of the controversial weapons since a Norwegian-brokered ceasefire broke down in 2006. The use of cluster bombs is contentious because of their ability to cause damage over a wide area. Also, many of their bomblets do not explode immediately, and the unexploded parts continue to pose a danger to civilians after fighting has ended.

Hospital repeatedly targeted

The 52 civilians reportedly killed were in an area — Sudanthirapuram in Mullaitivu district — near a government-designated safe haven exempt from military strikes. A further 80 people in the area were wounded, UN spokesman Gordon Weiss told reporters. But Weiss said some of the casualties also occurred in some areas inside the safe zone.

Fifteen UN staff and 81 of their family members who were stuck near the hospital were able to flee the area on Wednesday, Weiss said.

The Puthukkudiyiruppu hospital has endured strikes since Sunday, when artillery slammed into the hospital three times, killing nine patients and injuring 20. It was hit again Monday and three people were killed and 10 injured, said Sarasi Wijeratne, the spokeswoman of the International Committee of the Red Cross in Colombo, the Sri Lankan capital.

The fighting between government forces and the rebel Tigers has been concentrated in a small parcel of land called Vanni in Sri Lanka's northeast. Government troops have pushed steadily into the area in recent months in an attempt to crush the Tigers, putting Vanni's 250,000 inhabitants in the crossfire.

Dr. Thurairajah Varatharajah, the top health official in the war zone, estimated last week that more than 300 civilians had been killed in the recent fighting, something the government denied. Varatharajah has not updated his estimate.

Calls for ceasefire

Meanwhile, Canadian Foreign Affairs Minister Lawrence Cannon said Wednesday a ceasefire was needed for "the delivery of much-needed humanitarian assistance to civilians."

Canada "strongly condemns recent shelling attacks on the hospital in Puthukkudiyiruppu and firing into the government-designated safe area," Cannon said. "All efforts must be made to avoid civilian casualties."

Cannon said Ottawa believes that the conflict can only be resolved "through a durable political solution that meets the legitimate aspirations of all the people of Sri Lanka."

Canada also pledged $3 million in humanitarian aid to the country.

Liberal Foreign Affairs critic Bob Rae said the Conservative government has been too slow to react to the situation.

"… Frankly, I think, we're not playing the leadership role that I'd like to see us play," Rae said.

Other Western governments have also delivered sobering messages to both the government and the rebels. The United States and Britain released a joint statement calling on both sides to agree to a temporary ceasefire to allow civilians and wounded individuals to leave the conflict area and to give humanitarian agencies access to the war zone. Sri Lanka barred nearly all aid groups from the area last year.

On Tuesday, the United States, the European Union, Norway and Japan called on the rebels to consider surrendering to avoid more bloodshed.

Final airstrip captured

The military said it captured the Tamil Tigers' seventh and final airstrip Tuesday, effectively grounding their tiny air force and edging troops closer to ending the long-standing insurgency. Sri Lankan President Mahinda Rajapaksa, speaking Wednesday in a speech marking the 61st anniversary of Sri Lanka's independence from Britain, said the insurgents would be "completely defeated in a few days."

He made the remarks at a parade in the capital of Colombo as part of lavish celebrations to commemorate the event.

In recent months, Sri Lankan troops have routed the rebels in much of the territory in the country's northeast, which could end the Tigers' war for a separate homeland for the minority Tamils. The conflict, in the country's north and the east, started in 1983 and has cost more than 70,000 lives.

With files from the Associated Press