DAMASCUS — Lebanon’s Hezbollah and Syria’s army made big advances against insurgents in mountains north of Damascus on Wednesday, Hezbollah and Syrian state media said, shoring up President Bashar al-Assad’s grip on the border zone.

The Arab American News correspondent in Beirut, Nabil Haissam, learned from sources close to Hezbollah that the group’s leader, Hassan Nasrallah, will declare victory over the insurgents this weekend. 

The gains in the crucial Qalamoun region close to Lebanon against groups including the al-Qaeda-linked Nusra Front follow significant defeats for Assad elsewhere, notably in Syria’s northwest near the Turkish border.

Hezbollah fighters and the army seized Talat Moussa, the highest peak in the area targeted in the offensive. Sources briefed on the situation said that move had effectively secured control of the entire area some 30 miles from Damascus.

“Now only the final stage of the operation is left,” one of the sources said.

Syrian state TV credited the advance to the army and “the Lebanese resistance”, an unusual public acknowledgement of Hezbollah’s role in the battle for an area used by the insurgents to ferry supplies between Syria and Lebanon.

It also said that the army was pursuing the remnants of the insurgents in the town of Fleita.

Hezbollah has unleashed heavy firepower in the offensive, including concentrated rocket bombardments. The Syrian Observatory for Human Rights, a British-based group that tracks the conflict, said this had forced many insurgents to withdraw.

Syrian militants had launched cross-boarder attacks on Lebanese security forces. Hezbollah says it is participating in the war to guard Lebanon’s border.

ISIS battles army near world heritage

Despite advances on the Lebanese border, ISIS militants were fighting government forces near an ancient city, which is home to one of Syria’s world heritage sites, on Thursday, part of a major offensive in central regions by the jihadist group that has destroyed antiquities in Iraq.

ISIS fighters said online that the group was shelling an air base near Tadmur, an oasis in the desert north-east of Damascus also known as Palmyra.

One of the fighters said ISIS was also attacking areas around the town’s prison where some of its members are believed to be held. “The airport is also a major weapons depot. We want these weapons,” he said.

Syria’s antiquities chief, Maamoun Abdulkarim, said the fighting was just one or two km from Tadmur, warning that if the militant group seizes the city, “they will destroy everything that exists there.”

The Syrian Observatory for Human Rights said the militants had taken up positions outside Tadmur, which is listed as a UNESCO World Heritage site, after capturing al-Sukhna, 46 miles to the northeast, on Wednesday.

An army source said fighting continued in al-Sukhna for a second day on Thursday and troops were still in their positions.

It would be the first town taken by ISIS in direct fighting with government forces. Others seized by the group in the north and east were taken from other insurgents.

ISIS has in recent months mounted frequent attacks on government- and rebel-held areas to the west of its strongholds in Deir al-Zor and Raqqa provinces, where its fighters have been facing air strikes by a U.S.-led coalition.

Tadmur, which has previously been a frontline in the four-year-long Syrian conflict, was included in UNESCO’s list of World Heritage in danger in 2013, according to the UNESCO website. It contains the monumental ruins of a city that was one of the most important cultural centers of the ancient world.

The ultra-radical Islamist group has systematically destroyed antiquities in Iraqi territory it seized last year.

The military source said Syrian forces had inflicted heavy losses on what it said were many ISIS fighters targeting al-Sukhna. “They are attacking in large numbers like cattle with heads facing the ground,” the source said.

The army had yet to confirm losses in its ranks, the source added.

Syrian state media said ISIS fighters were being hit by Syrian army air strikes, adding that an ISIS convoy had been destroyed to the east of al-Sukhna.