Lebanon was preparing today to lodge a formal complaint with the United Nations. Security Council over the latest Israeli raid into the south in which three Syrian soldiers and one Israeli commando were killed together with at least five Palestinian guerrillas.

The 10-hour raid, the 19th this year, came as the role of the 6,000-man U.N. peacekeeping force (UNIFIL) stationed in southern Lebanon ran into criticism here for failing to prevent armed elements of Lebanese Christian leader Saad Haddad from infiltrating its lines Wednesday night and blowing up houses in several villages, resulting in the death of three persons.

A military spokesman in Damascus confirmed the death of three Syrian soldiers and the wounding of two others, and Israeli officials said they represented the first Syrian Army casualties during an Israeli raid into Lebanon, Washington Post correspondent William Claiborne reported from Jerusalem.

[In Washington, State Department spokesman John Trattner said the Syrian killings added a dangerous new dimension to the violence and criticized the Israeli raid, as well as Christian Lebanese and Palestinian challenges to UNIFIL's authority. He called upon all parties to respect the territorial integrity of Lebanon and to cooperate fully with the U.N. peacekeeping force "to allow it to fully carry out its mandate."]

The Israeli attack began at dawn this morning with a force of Army paratroopers and infantrymen, estimated by the Palestinians at 500 strong, storming four southern Lebanese villages seven to 10 miles across the border and blowing up a number of buildings, according to Palestinian and Israeli accounts.

Israeli sources said the main target of the raid was a series of bunkers and building on a hilltop over Mahmudia and that the Israeli force was airlifted by helicopters out of the country after the attack was completed.

The official Palestinian news agency said that only four persons were wounded in the attack, while Israeli losses were put at 17 dead or wounded. But reporters who visited the site of the raid later today quoted local Palestinian commanders as saying five Palestinians died while eyewitnesses said they saw at least 12 bodies.

The Israeli Army command said one Israeli soldier was killed and three others wounded while about a dozen Palestinians died.

The latest Israeli raid on Palestinian positions in the south followed by a day a series of others led by Israeli-backed Lebanese Christian militiamen who infiltrated UNIFIL-controlled territory to assault Palestinian positions there. The militiamen are commanded by Maj. Haddad, who controls a swath of Lebanese territory along the Israeli border.

This led to a charge by the official U.N. spokesman here, Samir Sanbar, that there may have been a dereliction of duty by some UNIFIL members in allowing the militiamen to carry out the attacks.

Lebanese Foreign Minister Fuad Butros has just asked for a strengthening of UNIFIL, whose mandate was renewed by the Security Council yesterday. Today, he said the attack showed the U.N. force was too small to carry out its task.

UNIFIL was formed in 1978 after a major Israeli invasion of southern Lebanon. It is charged with verifying the withdrawal of Israeli troops as well as maintaining the peace and helping the Lebanese government to restore its authority over the south.