World IN BRIEF : LEBANON : Civilians Flee in Fear of Army-PLO Clash

Thousands of Lebanese fled the port city of Sidon in fear of a showdown between the Lebanese army and Palestinian guerrillas in lawless south Lebanon, security officials said. The exodus began last week as troops prepared for their planned thrust today into the guerrilla heartland. But the Palestine Liberation Organization vows that its guerrillas will hold bases they say they need for attacks on the Israeli army and to defend Palestinian refugee camps. Political sources said that despite tough talk by both sides, compromise is still possible.