Artillery and rocket duels across the Israeli-Lebanese border escalated today following the killing of an Israeli Army major in a rocket attack by Palestinian guerrillas on the southern Lebanese town of Marjayoun.

An early-morning barrage raked the Israeli panhandle along the Lebanese border, injuring one civilian, and Israeli artillery returned the fire, according to the army command.

Palestinian guerrillas and Israeli-supported Christian militias in Southern Lebanon also exchanged artillery fire, with the militias shelling the port cities of Sidon and Trye. Five civilians were killed and 15 wounded, according to Beirut radio.

The shelling followed a heavy bombardment of Marjayoun yesterday in which the Israeli Army major was killed and an Israeli soldier wounded while they helped the militias clear land mines placed by Palestinians, according to Israeli spokesmen. Last week a militia armored personnel carrier hit a mine in the same area, killing three persons.

Today's shelling by Israeli artillery reportedly hit the villages of Ashiya and Rihan, just east of Zahrani river, where the Syrian Army maintains forward postions. Overnight, Israeli aircraft flew over Palestinian encampments, dropping flares to observe ground movements, and today more Israeli warplanes were reported over Beirut.

The Lebanese government closed Beirut Airport today in an apparent effort to shock Christian militias and Syrian peacekeeping troops into respecting a cease-fire appeal.

Only rarely has the country's only official international airport been closed since the end of the 1975-76 civil war. Because of Beirut's fading role as a Middle East travel hub, the government's gesture was taken more seriously than most of its decisions. In addition, the closure added to a general feeling of claustrophobia in Beirut.

Announced after Christian militia shells slammed into a runway last night, the ban was lifted to allow the national flag carrier -- Middle East Airlines -- to fly its planes out to safety.

Mortar rounds, apparently fired by Christian gunners at the airport in Beirut's Moslem half, bracketed the nighttime takeoffs of the three Boeing 707s, but pilots reported to the control tower that they had missed.

Daily artillery, mortor, rocket and heavy machine-gun exchanges have become a permanent part of city life along the unofficial line dividing the capital since the civil war.

The Syrians have bottled the Christians up effectively, stopping all normal business, social and political exchanges. Lost in the mists of charge and countercharges by now are the origins of the current round of fighting, but increasingly both Christians and Syrians are convinced that the other is embarked on a war of attrition.