Memories of Lebannon's deadly civil war were revived today with an increase in violence and a call by the Lebanese government for yet another cease-fire.

Reflecting increase concern, President Elias Sarkis decided to surround his mountain, suburban presidential palace with 10 tons of protective cement blocks and turn its ground floor into a bomb shelter.

Beirut Airport, which was shut down for five months in the final stages of the 1975-76 civil war, remained closed for the third day today because of rightist Christian shellfire. Meanwhile, Syrian peacekeeping troops rocketed Christian East Beirut.

Adding to the claustrophobic atmosphere was shelling that closed the port of Beirut -- reopened briefly this morning to permit two ships to go.

The Christians also fired tank cannons at the 23-story Murr Tower, an uncompleted office building that serves as a major fire base for the Syrian peacekeeping forces.

Elsewhere, Syrian and Christian militia gunners exchanged heavy-weapons fire along the line dividing the capital between its Christian eastern and predominantly Moslem western halves.

In the eastern Christian city of Zahle, bishops of various denominations appealed to President Reagan, Soviet President Leonid Brezhnev and French President Valery Giscard d'Estaing to help stop the fighting. Seven persons were reported killed in Zahle today in the first serious fighting there in a week.

Adding to the tension in Beirut, where a French-run hospital was hit by shells and caught fire along with a number of other buildings, factional fighting broke out in the western sector.There, along the once fashionable Hamra shopping street, at least 15 persons were killed in a shootout between gunmen from the Shiite Moslem Amal group, with leftist Christian allies and members of the Iraqi Baath movement.

According to clandestine radio stations run by rival militias in the divided city, a total of eight Lebanese were killed and about 36 wounded in the day's shelling.