Fierce fighting erupted during the night on the Syria-Lebanon border between Syrian troops and unknown gunmen, leaving a Lebanese man dead and four wounded, a Lebanese security source said on Sunday.
Lebanese President Michel Sleiman demanded on Sunday that Syria "refrain from firing towards Lebanese territory."
He also stressed, in a statement, the need to "respect the neutral position of (Lebanon) which means not interfering in the internal affairs of other countries, notably Syria."
The violence was triggered by the death hours earlier of another Lebanese man, who was killed on Saturday in gunfire coming from the Syria side of the border near a river separating the two countries, the security source said.
Members of his clan took part in the clashes against Syrian troops during the night in the Bukayaa region of northern Lebanon, a Lebanese official told AFP.
The Syrian army used artillery, mortars and automatic weapons fired from the Syrian village of Mcherfe as they clashed with the gunmen, according to the security source, who said a Lebanese man was killed and at least four others wounded in the fighting.
He was unable to say whether the gunmen were Lebanese or Syrians opposed to the regime of President Bashar al-Assad.
Since the Syrian uprising began in March 2011, there have been numerous deadly clashes along the northern and eastern borders of Lebanon, usually between the Syrian army and armed Syrian or Lebanese groups backing the rebellion against the regime in Damascus.
There have also been clashes between armed groups and the Lebanese army seeking to prevent the infiltration of fighters into Lebanon.
Beirut has officially adopted a neutral policy towards the Syria conflict, but it has deepened divisions in the country, with the Sunni-led March 14 movement supporting the revolt and the Shiite Hezbollah and its allies backing the Assad regime.
The violence has raised fears of the kind of sectarian strife that rocked Lebanon during its 1975-1990 civil war.