Israeli Prime Minister Menahem Begin expressed regret yesterday over any civilian casualties in Wednesday's Israeli air raids against southern Lebanon. But, he added, "we do not apologize for the operation itself."

The casualty toll from the Israeli attack was reported yesterday at more than 100 dead and 150 wounded, most of them civilians.

"We regret it very deeply." Begin told reporters after meeting with U.S. Ambassador Samuel Lewis.

The Israeli punitive strikes were aimed at Palestinian guerrilla bases in southern Lebanon following two days of Palestinian rocket attacks on Nahariya, in northern Israel, that killed three Israelis.

"To defend our people those air raids were carried out and if there is quiet on the other side, there will be absolute quiet on our side," Begin said. "If they attack us, there will be counterattacks.

"But we hope that now the ceasefire will be restored and again talks will be resumed on a permanent settlement for . . . Lebanon that will bring peace to Christians, Moslems and our own civilian population in the northern part of our land."

The American ambassador met with Begin to convey U.S. concern at the latest escalation of violence in southern Lebanon. Foreign Minister Moshe Dayan and Defense Minister Ezer Weizman attended the session.

In Beirut, Lebanese government officials accused Israel of "overt aggression" and said Lebanon would bring up the matter in the U.N. Security Council.

Lebanese and Syrian officials held a top level meeting in Beirut in an effort to prevent recurrence of fighting in southern Lebanon.

In Damascus, Syrian President Hafez Assad conferred with Yasser Arafat, chairman of the Palestine Liberation Organization (PLO).

Sources in Beirut said Syrian Foreign Minister Abdel Halim Khaddam has assured the Lebanese government that Syria would move quickly to "pacify" southern Lebanon, which is largely under Palestinian control.

One of the rightist Lebanese leaders, former President Camille Chamoun, warned yesterday against continued Palestinian presence in the south.

"Do they want to fight Israel?Why don't they attack it? If they don't want to attack why are they still there - only to invite tragedies?"

A leftist Lebanese daily, As Safir, meanwhile attacked the Christian rightists who "have lost the Lebanese civil war and see in Israel their only hope for achieving their goals."