Palestinian gunners entrenched in hilltop positions unleashed an intense barrage of artillery and rockets against Shiite-controlled approaches to three besieged Palestinian refugee camps at sundown today in an effort to break a four-day-old campaign for control of the guerrilla strongholds.

Militiamen of the Shiite Moslem Amal movement reportedly were in control of most of the Sabra camp but still advancing slowly into adjacent Shatila, where guerrillas holed up in underground hideouts were resisting with grenades and machine-gun fire.

Amal leader Nabih Berri called on guerrilla fighters entrenched inside a third camp -- Burj al Barajinah -- to surrender, but his men were unable to make any headway into it.

Meanwhile, shelling scattered mourners at a funeral service in Christian east Beirut for 38 victims of an unexplained car-bomb explosion yesterday. The Lebanese Forces Christian militia accused Palestinians of planting the bomb, but no group has claimed responsibility.

Rockets from Palestinian positions in the hills were heard thundering into Shiite neighborhoods near the Beirut airport road, in the vicinity of the refugee camps. State television, whose reports are often sympathetic to the Shiites, said several hundred surface-to-surface missiles were fired at Beirut quarters north and east of the refugee camps inflicting hundreds of casualties. There was no independent confirmation.

Middle East Airlines, Lebanon's flag carrier, announced it had canceled five scheduled flights to the Persian Gulf tonight after two persons were wounded by shelling in the airport perimeter.

Police said today that at least 200 persons have been killed and more than 1,600 injured since Sunday in the battle for the camps, but the figures were not considered complete.

Since Monday, the International Committee of the Red Cross has been able to enter the camps only twice for very brief periods and has suspended operations until a truce is reached and escorts provided by the warring factions.

The Shiites say they intend to prevent the Palestinian guerrillas from reestablishing themselves as a military power in the Beirut camps or in southern Lebanon. They say they fear this would subject Shiite villages in southern Lebanon to retaliatory Israeli attacks.

Although the Shiite militia has become closely allied with Syria in recent years, many of the Palestinians it is fighting in the camps belong to pro-Syrian factions that also are opposed to the leadership of Yasser Arafat.

Two Damascus-based guerrilla groups -- the Popular Front for the Liberation of Palestine and the Democratic Front for the Liberation of Palestine -- accused Amal of "committing massacres" against Palestinian civilians in the camps, Reuter reported.

In Amman, Palestine Liberation Organization leader Arafat also charged that Shiite fighters were committing "massacres and genocide" against Palestinians. He called the attack "a big conspiracy against our refugee camps and our people" that involved Israel, Syria and the United States.

Amal, saying it is fighting for the principle of keeping southern Lebanon for the Lebanese, finds itself abandoned by its closest allies of the last two years, the Druze Progressive Socialist Party, headed by Walid Jumblatt. Jumblatt has made no move to stop Palestinians from shelling Shiite areas from Druze territories.

Meanwhile, the Christian Lebanese Forces condemned "Palestinian terrorism," blaming it for a massive bomb that killed 60 persons and wounded about 200 in the Christian neighborhood of Sin el Fil yesterday. The Lebanese Forces charged that Arafat was trying to sow discord among the Lebanese to pave the way for his return.

Christian mourners gathered in Sin el Fil for a collective funeral service. President Amin Gemayel, a Christian who owns a residence in the neighborhood, stopped briefly. Crowds outside the church scattered and the funeral was shortened when shells landed nearby.