BEIRUT -- Syria's civil war spilled over into neighboring Lebanon once again on Sunday, with gun battles in the northern city of Tripoli between supporters and opponents of President Bashar Assad's regime that left four dead.

Nine Syrian judges and prosecutors also defected to the opposition. It was the latest setback for the regime, which appears increasingly embattled with rebels making gains in northern Syria and near Damascus, the capital.

Germany's Federal Intelligence Service chief Gerhard Schindler predicted the Assad regime would not survive.

"Signs are increasing that the regime in Damascus is in its final phase," he was quoted as telling the daily Frankfurter Allgemeine Sonntagszeitung.

In Geneva, the United Nation's Special Representative for Syria and the Arab League, Lakdhar Brahimi, met with Russian Deputy Foreign Minister Mikhail Bogdanov and U.S. Deputy Secretary of State William Burns to discuss the crisis in Syria. They said in a joint statement that the situation in Syria was "bad and getting worse," adding that a political process to end the conflict was "still necessary and still possible."

Russia and the United States have argued bitterly over how to address the conflict, which began with peaceful protests against Assad in March 2011 and escalated into a civil war that has killed an estimated 40,000 people. Activists said another 45 were killed on Sunday.

In Lebanon, fighting between pro-and anti-Assad gunmen flared as bodies of three Lebanese, who were killed after crossing into Syria to fight in the civil war were brought back home for burial, the state-run National News Agency said.

Four people were killed and 12 were wounded in the gunfights, the agency said. Two Lebanese soldiers were also injured, the Lebanese Armed Forces command said.

Syria civil war has often spilled into neighboring countries including Turkey, Lebanon and Israel, raising concerns of a wider war in the volatile region.

Lebanon, which Syria dominated for decades, is particularly vulnerable to getting sucked into the crisis. The two countries share a porous border and a complex web of political and sectarian ties.