(bbc) -- Government troops launched an offensive in Ras Baalbek, the last remaining ISIS stronghold in the country, on Saturday.

The army says there are about 600 militants in the mountainous region, which ISIS has held since 2014.

About 20 militants have been killed in the latest operation and 10 soldiers have been injured, the military says.

The offensive is aimed at ridding the area of ISIS militants who are armed with anti-aircraft and armour-piercing missiles and drones, the Lebanese army said.

Youssef Roufeyel, a resident of Ras Baalbek, told Reuters news agency the people of his village would do whatever was necessary for victory.

"This battle requires help and support from the people, and we are behind the army and by their side," he said.

The Lebanese army later posted an image on its website showing its troops waving both a Lebanese and a Spanish flag in Ras Baalbek in what it described as a "salute from our troops" to the victims of the Barcelona terror attack in which 13 people were killed on Thursday.

ISIS said it had carried out the attack, which took place in the city's famous Las Ramblas district, though it is not clear whether any of the attackers were directly connected to the group or simply inspired by it.

The latest operation in Lebanon comes as ISIS faces a number of military strikes on territory it controls in both Syria and neighbouring Iraq, where a brutal fight to rid Mosul of its militants left the city in ruins.

Militants have long been active in mountainous eastern Lebanon near the border with Syria, where a bloody war has raged since 2011.

Meanwhile, the Syrian army and the Lebanese Hezbollah, announced their own offensive against ISIS, though Lebanon said that the two operations were not connected.

(Photo: The Lebanese army posted an image as a "salute" to the victims of Thursday's Barcelona attack. LEBARMY.GOV.LB)