BEIRUT: Syrian regime forces on Sunday seized a strategic town as they pushed towards a militant-held airbase in an offensive to reclaim ground in northwestern Idlib province, a monitor said.

Government forces backed up by Russian air power are conducting an operation to carve out a foothold in the southeast of the province, the last one that had remained completely beyond regime control.

Troops captured Sinjar, the “biggest town in southeast Idlib,” from Syria’s former Al Qaeda affiliate and were within 14 kilometres of the Abu Al Duhur military base, the British-based Syrian Observatory for Human Rights said.

The base — which government troops lost to the militants in 2015 after a two-year siege — could provide President Bashar Al Assad’s forces with a vital forward post in the Idlib province.

The drive into the region is aimed at securing a key road that links Syria’s second city of Aleppo — recaptured by the government just over a year ago — to the capital Damascus, the Observatory said.

State news agency SANA reported on Saturday evening that the regime forces had taken control of “some towns and villages in the southeast” of Idlib province.

Since the start of the operation in late December, Assad’s forces have recaptured roughly 60 towns and villages on the border between Idlib and neighbouring Hama province, Observatory head Rami Abdel Rahman said.

In response to the situation on the ground the militants’ “military council” under leader Mohammad Al Jolani convened an “urgent meeting,” coalition Hayat Tahrir Al Sham said.

“The campaign by the criminal regime will not be easy,” said the group, dominated by the one-time Al Qaeda affiliate, previously known as Al Nusra Front.

More than 340,000 people have been killed in Syria and millions displaced since the conflict began in March 2011 with anti-government protests.

Russia’s intervention in support of Assad has shifted the balance firmly in the regime’s favour.

Meanwhile, experts said Syria’s rebel-held enclave of Eastern Ghouta near the capital is the regime’s Achilles heel, and because of this it faces an almost inevitable military offensive.

The battle-scarred region east of Damascus, which has been under near-daily bombardment and a crippling government siege since 2013, is strategically vital to Assad.

Despite residents facing a humanitarian crisis, rebels controlling the region have been able to use it as a launch pad for rocket and mortar attacks on the capital.

Joshua Landis, director of the Centre for Middle East Studies at the University of Oklahoma, said the ongoing rebellion in Eastern Ghouta contrasted with the regime “presenting itself as the winner” of Syria’s war elsewhere.

“The persistence of the East Ghouta resistance has become a major embarrassment and liability for the Assad regime,” he said.

The Assad regime, militarily backed by its ally Russia, has retaken control of more than half of the country with a string of victories against rebel and militant forces.

“It hopes to convince the international community that it faces little opposition any more save for the enclaves on the margins of Syria,” Landis said.

But rebel and militant groups managed this week to surround a regime base on the edge of Eastern Ghouta, prompting intensified regime air strikes there.

Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, said the enclave is the regime’s “weak spot.”

“The factions there are strong and directly threaten Damascus,” he told AFP.

Even though Eastern Ghouta was one of four “de-escalation zones” agreed under a deal between rebel and regime backers, fighting has continued there.

The area is the target of near-daily regime air strikes and artillery fire that has killed thousands of people since 2011. Rebels have killed hundreds of civilians with mortar rounds and rockets fired at Damascus, although such attacks have waned since the regime seized several areas close to the capital.

The beleaguered 100-square-kilometre  enclave’s estimated 400,000 inhabitants are suffering severe shortages of food and medicine.

Children there are particularly vulnerable to malnutrition.

Despite the civilian suffering caused by the blockade, rebel groups in Ghouta “still have a popular base, because thousands of their fighters are from the region,” Abdel Rahman said.