BEIRUT, Lebanon (AP) _ Gunmen killed a Moslem army officer and a pro-PLO politician in separate attacks today, and Moslem and Christian militias clashed along Beirut's dividing Green Line.

Four or five assailants intercepted Maj. Ibrahim el-Far, 42, as he drove to work through Moslem west Beirut at 8 a.m., police said. They forced him out of his car, bundled him into their car and sped off.

His gunshot body was found an hour later near Beirut's bomb-ravaged port, authorities said.

El-Far was the third Sunni Moslem officer with the army's intelligence department to be killed or kidnapped in Moslem west Beirut in one month. Police said the attacks suggest a Moslem militia was targeting Moslem officers serving with the 37,000-member Lebanese army because its command is dominated by Christians.

Maj. Amin Kassem, 37, was shot and killed in his car April 9 and Capt. Riyad Doughan was kidnapped Friday. Doughan was freed Sunday after the army command closed all crossings between Christian east Beirut and the Moslem western sector, and threatened to keep them shut unless he was released.

Also today, gunmen raked the car of lawyer Nassih Khatib, 45, with machine gun fire as he drove through the central mountain town of Mdeirej, police said. He was killed along with three bodyguards. Police said the car was struck by more than 100 bullets.

Khatib was a founder of the pro-Syrian Arab Democratic Party and its Arabian Red Knights militia. He left the party in 1980 and has since been close to the Palestine Liberation Organization.

One civilian died and six were wounded in today's fighting in Beirut, police said. Christian and Moslem militias clashed with mortars, rocket- propelle d grenades and machine guns in the pre-dawn battle.

Each side accused the other of starting the clash.

In other developments, the wife of an 85-year-old kidnapped Frenchman pleaded with his captors to be ''gentle and caring because he is so old and half-deaf and needs a hearing aid.''

Camille Sontag was abducted Wednesday by two gun-wielding gunmen from a crowded boulevard in west Beirut.

''I am confused. I want my husband to come back. We were about to leave in a week,'' Blanche Emmanuelle Sontag, also 85, told reporters from her west Beirut home. ''What do they want from him. He is old and weak.''

No group has claimed responsibility for Sontag's abduction or for the kidnapping Wednesday of a Lebanese Christian professor at the American University of Beirut.

University officials announced a day-long suspension of classes to protest the abduction of Nabil Matar, 36. The faculty and about 200 students today staged a silent march on campus to protest attacks on staff and students.

Most of the university's Western professors have fled west Beirut since the body of an American university librarian and two Britons were found outside Beirut last month. A note said they were killed in retaliation for the U.S. air raid on Libya April 15.