BEIRUT (AP) — Lebanon's official news agency says four people have been killed in fighting in the Lebanese city of Tripoli between gunmen loyal to opposite sides in Syria's civil war.

The state-run National News Agency says 12 others were wounded in the clashes Sunday. Tripoli has been the scene of frequent sectarian clashes during the Syria civil war.

The fighting has sometimes spilled across Syria's borders, raising concerns of a regional war.

Last week the Lebanese army sent additional troops to Tripoli to try to prevent clashes that followed reports of 17 Lebanese men killed after entering Syria to fight alongside the mostly Sunni rebels. The Syrian rebels are trying to topple President Bashar Assad, whose regime is dominated by Alawites, an offshoot Shiite group.

Tripoli has sizeable Sunni and Alawite communities.