Syrian troops yesterday pulled out of key positions in Christian East Beirut and were replaced by Saudi soldiers as part of an Arab plan to stop Syrian-Christian fighting and restore peace to Lebanon.

The moves dramatically lowered tension in the battered eastern sector and raised hopes that nine months of recurring clashes between Syrian units of the Arab peacekeeping force and right-wing Christian militiamen may now be over.

But machine gun and sniping duels continued between Syrian and militia positions across the no-man's-land dividing Christian East and Moslem West Beirut. Moreover, rightist leaders, while welcoming the Syrian pullout, cautioned that it was only "one step in a long march" and repeated that their goal is the withdrawal of all foreign armies from the country.

But even the most hard-line rightist militia chiefs appeared to take a more conciliatory line. Buoyed by what they regard as a moral and "tactical" victory over the Syrians, the rightist leaders said they would try "political means" to achieve their goal, and they appealed to their Lebanese Moslem foes to join them in negotiations to settle long-standing differences.

Starting at dawn, about 500 Syrian soldiers left their sandbagged positions in several buildings commanding two key bridges from East Beirut to roads leading into the traditional Christian heartland of Mount Lebanon to the north. The Karantina and Nahr bridges had been the scene of pitched battles with militiamen during the heavy Syrian shelling earlier this month, and intermittent sniping since the Oct. 7 cease-fire.

Syrian units also pulled out of the Rizk Tower, the tallest building in East Beirut, whose upper stories they had used to pour streams of rocket and missile fire into surrounding neighborhoods.

As the Syrians left both places, several truckloads of furniture and other goods looted from surrounding apartments and businesses went with them. Officers were seen driving away in private cars.

At the bridges, departing Syrian soldiers waved from their trucks to residents, who waved back muttering curses under their breath.

In Beirut's Armenian quarter, which borders the strategic bridges, residents complained that both the Syrians and the Christian militiamen looted abandoned properties and extorted protection money from businesses and factories.

The quarter's 125,000 Armenians largely tried to stay out of the Syrian-militia fight as they stayed out of the 1975-76 civil war. But their neighborhoods got caught in a crossfire and suffered some of the worst damage in the latest shelling. Residents said 50 Armenians were killed and about 300 wounded. More than half the populace has fled to safer areas.

The approximately 150 white-helmeted Saudis who took over the Syrian positions at the bridges were widely welcomed, but seemed somewhat bewildered by their task as traffic jammed the crossing for the first time in weeks.

The Syrians still hold two bridges across the Beirut river in a southeastern suburb of Beirut, where many of the withdrawn troops and equipment have been gathered. Syrians units also retain their heavy gun emplacements in the surrounding hills, giving them their heavy gun emplacements in the surrounding hills, giving them an undiminished ability to shell Christian districts in any new fighting.

Although the redeployment was worked out by an Arab foreign ministers' conference this week to consolidate the earlier cease-fire, militia leaders took credit for the move.

"The Syrians were forced to withdraw," overall Christian militia commander Beshir Gemayel said.