Moslem gunmen killed at least four passersby in a hit-and-run raid within the Christian section of Beirut yesterday, a broadcast by the Christian Phalangis Party said.

It was the second attack within the Christian area in two days. An explosion outside a Christian militia barracks killed 35 persons and injured more than 50.

The Phalangist radio said Christian militiamen captured the gunmen who carried out yesterdays attack. In the car used by the attackers were found explosives and files belonging to the Communist action organization, the Christian broadcast.

The phalangis radio said "black phantoms of disarray" were trying to reignite the civil war between Christians and Moslems.

Lebanon's coalition of leftist parties, which includes the Communist action group, issued a statement denying involvement in the attacks.

There were these other developments involving the Middle East:

The Palestine Liberation Organization accused "Zionist agents" of assassination Palentinian militant Mahmoud Saleh outside his bookshop in Paris Monday night.

President Anwar Sadat of Egypt told a visiting group of Palestinian leaders that the Arabs would boycott any resumption of the Geneva conference on the Middle East unless the Palestine Liberation Organization is invited, the authoritative Cairo newspaper, Al Ahram said.

Scores of small boats hooted a welcome and hundreds of well-wishers cheered as Abie Nathan and his Peace ship arrived at Eitat, an Israeli port on the Red Sea, after sailing through the Suez Canal.