Mortar fire killed at least 14 Rwandans and wounded 150 in a church compound where they had taken refuge from heavy fighting in the capital Kigali, aid workers said Monday.

At least two mortar bombs exploded late Sunday near the Sainte Famille church, said Moctar Gueye of UNAMIR, the U.N. Assistance Mission in Rwanda. "We were not able to detect exactly who shelled the camp."Kigali, where government forces are battling advancing rebels of the Rwanda Patriotic Front, suffered "one of the heaviest days of shelling we have seen," said Patrick Gosser of the International Committee of the Red Cross.

"Mortars didn't hit the church itself. They hit the surroundings, and people were hurt in a market area," he said.

At least 14 were killed outright, he said. Some 60 of the wounded were transported to the ICRC's makeshift hospital, set up to cope with horrific casualties in recent weeks, and others were taken to Kigali's central hospital.

"I don't know how many were left behind who didn't have a chance," said Gosser.

Hospital facilities are overstretched in a city where the United Nations estimates some 20,000 bodies are lying unburied.

The United Nations says about 2,000 mainly Tutsi civilians are clustered around Sainte Famille where they have sought refuge from marauding pro-government Hutu militias since chaos erupted in the wake of President Juvenal Habyarimana's death in a rocket attack on his plane on April 6.

"They are running from certain death," said Gueye.

UNAMIR peacekeepers protect about 14,000 civilians in buildings around the city, but the militias issued fresh threats last week to butcher these people, officials said.

UNAMIR troops visited the Sainte Famille area Sunday, but they are not there permanently. The ICRC said government authorities had posted police to guard the area.

On April 19, government forces fired mortars at the U.N.-guarded Amahoro sports stadium in the RPF-controlled part of Kigali where some 5,000 people are sheltered, killing some 60, U.N. officials said.

Aid officials are struggling to provide supplies for up to 250,000 refugees who fled from Rwanda into northwestern Tanzania as the RPF advanced in recent days.

The flood of refugees dried up over the weekend, but the RPF denied allegations that it had formally closed the border.