Lebanese officials say sectarian gun battles linked to the civil war in neighboring Syria have killed another four people in the northern city of Tripoli.

Authorities said Sunday's fighting involved Sunni supporters of Syria's rebels in the Tripoli neighborhood of Bab Tabbaneh and Alawite loyalists of Syrian President Bashar al-Assad in the adjacent district of Jabal Mohsen.

Gun battles between the rival neighborhoods have killed at least 13 people since early last week. The violence began after reports emerged that Syrian government troops ambushed and killed a group of Lebanese Sunnis from Tripoli who crossed into Syria to join the rebels last month.

The killings inflamed long-running sectarian tensions in Tripoli, whose Sunni majority is sympathetic to Syria's predominantly-Sunni rebels and whose Alawite minority is allied to Alawite Syrian President Assad. The Lebanese government has sent reinforcements to Tripoli to try to stop the violence, which has erupted several times in recent months and raised concerns that Lebanon could be dragged into Syria's conflict.

Syrian authorities returned the bodies of three Lebanese Sunnis killed in the ambush to Lebanon on Sunday. Beirut has asked Damascus to repatriate the bodies of all the fighters.

In the latest fighting in Syria, the Britain-based Syrian Observatory for Human Rights said rebels captured most of a Syrian military base near the northern city of Aleppo on Sunday. It said several rebels and soldiers were killed in the battle at the Sheikh Suleiman compound, while about 140 government troops escaped.

There was no independent confirmation of the fighting because Syria tightly restricts independent reporting.

U.S. and Russian diplomats met with U.N. peace envoy Lakhdar Brahimi in Geneva on Sunday to try to find a political solution to the Syrian conflict. Washington wants Mr. Assad to quit and begin a transition to a democratic government, while Moscow opposes Western demands to impose regime change on the Syrian president, a longtime Russian ally.

Russian Foreign Minister Sergei Lavrov said Sunday Moscow's participation in the Geneva talks does not mean it has softened its position. He said Russia is not conducting any negotiations on the fate of Mr. Assad.