Several hundred Syrian-controlled Palestinian troops took positions in sensitive sectors of Beirut yesterday as sniper fire punctured a fragile truce between Syrian forces and rightist militiamen.

Palestinian sources said units of the Palestine Liberation Army, moved in from Syria over the past few days, had been deployed along a line splitting Beirut into a Christian eastern half and a Moslem west.

The sources said the deployment was a warning to President Elias Sarkis not to press too vigorously his reported plan for thinning out Syrian troops in and around east Beirut.

Syrian troops and rightist militiamen have waged increasingly savage battles on the east side of the city. A truce arranged last Friday by Sarkis and Syrian President Hafez Assad was still holding.

Sarkis met in Jordan yesterday with King Hussein after talks in Syria and a Persian Gulf tour in preparation for a conference next Sunday of countries contributing troops or funds to the Arab League peace force in Lebanon.

In Metullah, Israel, United Nations sources reported a French soldier serving with U.N. forces in Lebanon was shot and killed in a clash with Palestinian guerrillas Tuesday night.

They also said two Austrian soldiers with U.N. forces in the Golan Heights was killed by another Austrian soldier who ran amok, then shot himself.