BEIRUT, Lebanon--Gunmen killed an Iranian envoy and foiled a mercy mission yesterday when they fired on two U.N. trucks carrying food to besieged and hungry Palestinian refugees, police reported.

They said the Iranian was in an ambulance accompanying the two trucks into the Bourj el-Barajneh refugee camp, which has been under siege by the Shiite Moslem militia Amal for 11 weeks.

The ambulance managed to enter the camp as the gunmen opened fire with automatic weapons, police said.

"The Iranian delegate was hit in the head and died later," they said. The identity of the Iranian was not immediately available.

The Iranian Embassy in Beirut could not immediately be reached for comment.

The ambulance left the shell-battered camp on Beirut's southern outskirts shortly before dusk without evacuating any wounded Palestinians.

Witnesses said the trucks came under fire a few yards from the entrance to the camp, which has been ringed by Amal forces since November 24. There have been reports that many of the camp's estimated 35,000 residents are malnourished and that some are near starvation.

Police said the gunmen shot the trucks' tires out. One witness, who declined to be identified by name, said the drivers jumped out and ran for cover.

A Palestinian spokesman, who declined to be identified, blamed Justice Minister Nabih Berri's Amal fighters for the shooting.

Amal accused the Palestinians of firing at the food convoy from inside Bourj el-Barajneh.

The United Nations Relief and Works Agency, which sponsored the relief mission, also donated two truckloads of food supplies to Shiite Moslems living in slums around the camp, police said.

The foiled mission came after daylong clashes in Beirut and an Israeli air raid against Palestinian positions in south Lebanon.

Some PLO officials have said inhabitants of Bourj el-Barajneh had resorted to eating cats, dogs and rats. Reporters have not been able to verify these reports because they were not allowed through the Amal lines to enter the camp.

But 12-year-old Fadi Shaker, who sneaked out from the camp, told journalists: "Almost every man, woman and child has eaten cats or dogs, donkeys or mules. Now there's a shortage of animals."

Berri had earlier promised to order a 1-hour truce in the fighting around Bourj el-Barajneh to allow supplies in, provided an equal amount of food was sent to his Shiite community.