A Lebanese army officer was shot dead in the country's second city of Tripoli during fighting between rival sects on Thursday, a security source and state media said.

Lebanon's National News Agency said masked men on a motorcycle had opened fire on the officer, Fadi al-Jbaili, at around 6:30 a.m. (0430 GMT), killing him instantly.

Fighting between Tripoli's Sunni Muslims and members of the Alawite sect, an offshoot of Shia Islam, has killed at least 28 people over the last two weeks.

Long-running tensions between the two sects have been made worse by the three-year-old conflict in neighbouring Syria, where mostly Sunni rebels are fighting to overthrow President Bashar al-Assad, an Alawite.

Lebanon, beset by its own internal sectarian divisions and still recovering from a 1975-90 civil war, has struggled to control the violence in Tripoli.

On Wednesday, at least three people were killed in fighting in the northern coastal city, including an 11-year-old boy.

Another officer in Lebanon's security forces escaped without injury when gunmen opened fire on him, the National News agency reported on Thursday.