Militants ambushed a Lebanese army patrol near the border with Syria on Tuesday, killing six Lebanese soldiers and wounding one, a Lebanese security official said.

The attack occurred in a remote region of Ras Baalbek in eastern Lebanon and was followed by fierce clashes between the two sides, said the official, speaking on condition of anonymity because he was not authorized to talk to media.

The state-run National News Agency also reported the ambush, saying several soldiers were killed and wounded. It said the Lebanese military called in air support to the area.

It was not immediately clear who was behind the attack, which targeted the soldiers as they were moving from one post to another in the Tal Hamra area. Lebanese soldiers have been battling Syria-based Islamic militants, including the extremist Islamic State group and the Nusra Front, in areas near the border with Syria.

Local media said dozens of militants took part in the attack.

In August, the militant groups seized some 20 Lebanese soldiers and police officers during a brief cross-border raid on the Lebanese border town of Arsal. The extremists have already killed three of the captives, beheading two of them.

The plight of the remaining captive soldiers and policemen and their families has gripped Lebanon in the past weeks. Relatives of the hostages are staging an ongoing sit-in and blocking roads in Beirut to pressure the government to negotiate with the militants.