A booby-trapped car exploded yesterday in Moslem West Beirut, killing about 15 persons and injuring more than 20 others, police reported.

The blast gutted a pharmacy and shattered the glass of nearby buildings in the densely populated quarter of Basta al Fauqa, Beirut's state radio said.

Lt. Ahmed Khatib, leader of the breakaway leftist Lebanese Arab Army, claimed the explosion was an attempt on his life masterminded by Lebanese Army intelligence. He said he was driving by as the car blew up and barely escaped injury.

Elsewhere in the Middle East, former Israeli foreign minister Moshe Dayan spoke further about the disagreements that led to his resignation last week. He said the line the government wants to follow after the five-year period of self-government for Palestinians in the occupied territories would mean Israeli annexation of the West Bank and Gaza Strip.

"I couldn't participate or be responsible for the autonomy negotiations because this stand goes against my viewpoint," Dayan told Israeli Radio Friday.

U.S. Middle East mediator Robert Strauss, meanwhile, said yesterday in London he was encouraged by the newest round of Israeli-Egyptian negotiations and believes the May 1980 target date for an agreement on Palestinian autonomy can be reached.