The leader of the militant Hezbollah group said Sunday that the region is facing “unprecedented danger” from extremist groups and vowed his militants will expand their involvement in Syria’s civil war in support of government forces.

Sheik Hassan Nasrallah spoke during a ceremony marking the 15th anniversary of Israel’s withdrawal from southern Lebanon, vowing to battle Sunni extremists groups such as the the Islamic State of Iraq and Syria (ISIS). and al-Qaada. He said such factions are an “existential threat” to anyone who does not agree with their ideology.

Hezbollah openly joined President Bashar al-Assad’s forces in the civil war in 2013 and its fighters have been taking part in a major battle in recent weeks against jihadis in the Qalamoun mountain region that borders Lebanon.

“Our presence will grow whenever it is required for us to be present,” Nasrallah said in comments that came after Assad’s forces suffered several defeats over the past two months – mostly in the northwestern province of Idlib and the southern region of Daraa. The western city of Palmyra, home to a set of historic Roman-era ruins, was captured by ISIS last week.

“We are present today in many places and I tell you we will be present wherever this battle requires. We are up to it and we are the men for it,” Nasrallah said speaking from a secret location on a giant video screen.

Inside Syria, a military helicopter crashed earlier Sunday at the northern air base of Kweiras, killing all of its crew, state TV said, as an activist group said it was shot down by Islamic State militants.

The TV report quoted an unnamed military official as saying that the helicopter crashed as a result of a technical problem while taking off. The report did not say how many crew members were onboard at the time of the crash.

The Britain-based Syrian Observatory for Human Rights said ISIS militants who have been laying siege to the base for months shot down the helicopter.

Kweiras military air base is in the northern province of Aleppo and is close to the town of al-Bab, which is held by ISIS.

ISIS posted a statement on a militant website claiming responsibility for downing the Syrian helicopter.

Syrian rebels have shot down helicopters in the past.

Meanwhile in Damascus, a bomb exploded Sunday morning near the city center killing a brigadier general and six of his bodyguards, the Observatory said. It added that the attack was claimed by the ultraconservative Ahrar al-Sham group.

The Damascus media center identified the officer as Brig. Gen. Bassam Mehanna al-Ali.

State news agency SANA reported that a bomb exploded in the area without giving further details.