Syria’s conflict has regularly spilled over into Lebanon, with which it shares a long and porous border.
Syrian rebels regularly move across the border, transporting arms, as do fighters from the Lebanese Shiite movement Hezbollah, which has dispatched forces to bolster the regime against the uprising.
There were no casualties in Friday’s the gun battle, which came after at least one person in Lebanon was killed by shelling from Syria and a deadly rebel attack against Syrian forces launched from Lebanon.
“Lebanese army forces exchanged fire with gunmen near an army checkpoint in an area near the town of Wadi Khaled,” the security source said.
He added that the gunmen, believed to be Syrian, had escaped afterwards.
The fighting came after a barrage of at least 14 shells fired from Syria hit the Akkar border area of Lebanon, killing a Syrian man and wounding three Lebanese citizens, the source said.
The Syrian Observatory for Human Rights meanwhile said rebels had launched an attack from Lebanese territory against two villages near the Syrian town of Talkalakh.
The Britain-based group said five regime forces, including soldiers, border guards and pro-government militiamen, were killed.
In northern Syria, meanwhile said at least 16 people were killed in three regime aerial attacks on parts of Aleppo city, the Observatory said.
It said one of the attacks involved the use of explosive-packed barrel bombs dropped from helicopters, which the regime also used in central Hama, Damascus province and northwestern Idlib province on Friday.
Meanwhile, rebels took control of the village of Swisah in Quneitra, several kilometres from the ceasefire line that divides the Syrian-controlled Golan Heights from the Israeli-occupied sector.
The Observatory reported fierce fighting in the area between regime forces and rebel fighters.
More than 130 000 people have been killed since the Syrian conflict began on March 2011, and more than 2.4 million Syrians have become refugees.
More than 900,000 Syrians have fled to Lebanon ( a country of 4 million people) since the civil war erupted nearly three years ago. Many border towns and villages reportedly have now more Syrians than Lebanese inhabitants. The figure does not include the hundreds of thousands of Syrian workers who regularly cross the border to earn their living in Lebanon.