Two U.S. marines were killed by incoming rocket fire on their positions in Beirut at dawn today and two others were wounded by the barrage, a Pentagon official reported early this morning.

Lt. Col. Peter Friend said that the names of the marines were being withheld until their families have been notified. Details of the attack were not immediately available.

The marine positions near the Beirut airport have come under heavy fire during the past week as the sectarian violence in Lebanon escalated. Two marines were killed and 14 wounded Aug. 29 during a barrage of rockets and mortars. Other injuries were reported last week and four marines were wounded slightly yesterday when shells landed on their positions. The marines, who are part of an international peace-keeping force, used mortars to return the fire sporadically.

The shelling is part of heavy fighting involving Christian and Druze militias and the Lebanese Army following the withdrawal of Israeli troops to new positions to the south.

Washington Post correspondent Herbert H. Denton reported on that fighting yesterday from Beirut:

Artillery shells crashed continuously into mostly Christian east Beirut, the southern suburbs and mountains outside the city as the situation further deteriorated.

A producer for ABC-TV announced Monday afternoon that two of the network's technicians were missing in the hills above the capital and that a wounded Canadian television correspondent who had been with them was temporarily stranded there, unable to get transportation to a hospital because of the heavy shelling. NBC-TV said it had not heard from another crew since it went to the mountains on Friday.

The Associated Press quoted police sources as saying 31 people, including three Lebanese soldiers, were killed in Monday's fighting, and that 83 had been wounded. The casualties brought the unofficial toll to 82 dead and 216 wounded in two days since the Israeli pullout began. The AP also said two members of the ABC crew were wounded.

Lebanese Army armored units inched along the coast highway under heavy artillery barrages from Druze militiamen as Christian Phalangist militiamen sharply criticized the government for not sending the Army to take control in the mountains.

The indications this evening were that Druze militiamen had nearly succeeded in seizing a key Phalangist stronghold along the vital Beirut-to-Damascus highway.

The Druze, who have strongly opposed the Army's entry into the mountains, were exultant about their advance, raising faint hopes that this success might bring them to the bargaining table for an agreement to allow the Army to go to the mountains unopposed.

However, Druze spokesmen here sought to direct public attention to their claims that Phalangists had killed the village sheik and more than 40 civilians in the mountain town of Kfar Matta, another center of heavy shelling and fighting and an area where their positions had been overrun by Phalangists and the Army.

Beirut radio said Adel Hamiyeh, the minister of finance and the only Druze in the Lebanese Cabinet, resigned, United Press International reported. Other Druze sources said he was protesting the killings in Kfar Matta.

Last week Phalangists said Druze had killed the village priest and more than 40 civilians in the Christian town of Bmariam in a Syrian-controlled area of the mountains.

Lebanese government spokesmen confirmed both incidents but said each had involved fewer than a dozen deaths.

Sharp escalation in the civil strife came in the wake of Israel's pullout from the mountains early Sunday to consolidate positions in southern Lebanon.

Today, Beirut was rife with allegations that, before leaving, the Israelis had aided warring Christians and Druze, both, at various times, allies of Israel. Druze allies and a usually well-informed western diplomat said departing Israelis had permitted Druze militiamen to take over critical positions on the Beirut-to-Damascus highway. A Lebanese intelligence officer talked of information indicating that the Israelis had allowed Phalangists to bring in reinforcements at other locations on the thoroughfare.

"We have enough weapons, frankly," Alfred Mady, a member of the Phalangists' political bureau, told reporters Monday, "but we can get ammunition from Israel--at a price. Nothing's free."

Mady said the Lebanese Forces Christian militia was disappointed that the Lebanese government had not decided to send the Army into the mountains to fill the vacuum left by the Israelis' departure.

His observations came amid several reports that Druze had advanced into the town of Bhamdun, a Phalangist stronghold near the Beirut-to-Damascus highway. Druze control of the town would enable them to link up positions and control a stretch of the highway between the capital and Syrian Army positions to the east.

Mady and Phalangist radio accused the Druze of relying on the aid of Palestine Liberation Organization renegades, Libyans and Syrians in the attack. Druze militia spokesmen denied that.

For their part, Druze spokesmen claimed the Phalangists, in league with the Army, were responsible for the deaths at Kfar Matta.

The town of Kfar Matta is where seven ABC-TV employes sought shelter Sunday in the midst of heavy shelling following the Israeli withdrawal. After their cars were shot up and a shell landed on the house where they were hunkered down, they decided to run for safety. Clark Todd, the Canadian television correspondent with them, was wounded in the chest. A cameraman and soundman got separated from the others as they ran. The cameraman and soundman were still missing late Monday.

Todd, who urged the others to leave him, later was found by Lebanese soldiers who tended to his wounds. These turned out to be not as serious as had been thought at first. The soldiers waited for a lull in the shelling to take him to a hospital in Beirut.