In the long-running Syrian civil war, now in its ninth year, the northwestern region — where Turkish, Russian, U.S. and Iranian interests are at stake — has taken center stage in the conflict.

An all-out offensive by Syrian government forces to capture Idlib in northwestern Syria from insurgents could yet unleash an unprecedented humanitarian crisis, for the area is home to 3 million people.

Ten of thousands of people have fled to the Turkish border in the last few days as the Syrian army pushed a major advance further into the opposition's last major stronghold, residents, rights groups and opposition sources said on Wednesday.

They left Maarat al-Numan, a main city in Idlib province that has been a sanctuary for families fleeing former rebel areas, as a Russian-led campaign has come close to capturing the strategic town of Khan Sheikhoun further to the south.

Open gallery view Syrian civil war in the northwest, areas of control as of June 17, 2019 Credit: Reuters

Turkey, which is already hosting more than 3.6 million Syrian refugees, is facing strong pressure from Syria, Iran and Russia to deliver on its pledge to control the armed rebel factions in Idlib.

But Turkey also needs Russia to rein in Syrian President Bashar Assad to prevent a massive outflow of refugees and to keep Turkish soldiers on the ground safe.

The main insurgent group in the Syrian province of Idlib pulled out of a key rebel town as government forces advanced in the area on Tuesday amid intense bombardment and airstrikes, a militant group and opposition activists said.

As the militants withdrew, government troops moved into northern and western neighborhoods of Khan Sheikhoun, marking a significant gain for Assad’s forces as they try to chip away at territory controlled by the opposition in Idlib. The northwestern province, dominated by an al-Qaida-linked faction, is the last major rebel-held bastion in Syria.

The Britain-based Syrian Observatory for Human Rights, an opposition war monitor, said the al-Qaida-linked Hayat Tahrir al-Sham and other insurgent groups withdrew from Khan Sheikhoun as well as the towns and villages south of the town.

According to the Observatory, Khan Sheikhoun was home to about 1 million people, nearly 700,000 of them displaced by fighting in other parts of the country, before the government offensive began in April. In recent days hundreds of civilians remained in the town according to the group that tracks Syria’s war, now in its ninth year.

The Syrian Response Coordination Group, a relief group active in northwestern Syria, called on Tuesday for a “humanitarian truce” to allow civilians who are stuck in the areas of fighting to leave. The group said in a statement the Russia and Syrian governments “are practicing terrorism against civilians” in violation of international laws.

Khan Sheikhoun was a stronghold of the al-Qaida-linked militant faction, the most powerful group in rebel-held areas in Syria. The town was also the scene of a chemical attack on April 4, 2017 that killed 89 people.

Demilitarized zone

Turkish President Recep Tayyip Erdogan and Russian President Vladimir Putin “have an incentive to cooperate and ensure that nobody’s interests are totally trampled,” says Aaron Stein, the director of the Middle East program in American think-tank Foreign Policy Research Institute.

In September, the two leaders brokered a cease-fire for Idlib in the Russian resort of Sochi, preventing a bloody onslaught, despite the fact that Russia has firmly backed Assad and Turkey supports opposition forces. Nine months later, the truce has failed.

The agreement called for a 15-to-20 kilometer (9-to-12 mile) demilitarized zone free of insurgents and heavy weaponry and for two key highways crossing through Idlib to be reopened. The demilitarized zone has been breached and the highways are at the center of the current government offensive.

The U.S.-Turkey axis

The latest Syrian government gains come as NATO allies Turkey and the U.S. are discussing setting up a buffer inside Syria — one that Ankara wants to push Syrian Kurdish fighters it considers terrorists further to the east.

There has been speculation, meanwhile, that Russia and Turkey, which back rival sides in Syria’s conflict, have reached an agreement that would allow the Syrian army to retake parts of Idlib and reopen a highway that links the capital, Damascus, with the northern city of Aleppo, Syria’s largest.

Khan Sheikhoun, which had been held by militants since 2014, sits on that highway.

After the capture of Khan Sheikhoun, Syrian troops are likely now to move north toward Maaret al-Numan, another town on the highway that has been subjected to intense airstrikes over the past days. Opposition activists also reported intense bombardment on the rebel-held town of Jisr al-Shughour on the southwestern edge of Idlib on Tuesday.

Turkey will not move the military observation post in northwest Syria that a Turkish convoy was trying to reach when it came under attack during an offensive by the Syrian army, Foreign Minister Mevlut Cavusoglu said on Tuesday.

An air strike on the Turkish military convoy on Monday killed three civilians as it was heading south towards the observation point, Turkey's defence ministry said.

"Right now we don't have an intention such as moving this elsewhere," Cavusoglu told reporters in Ankara. "It will carry on with its mission," he said, adding that necessary security and military measures were being taken.

The observation point was one of 12 set up by Turkey in northwest Syria under an agreement with Russia and Iran aimed at reducing fighting in Syria's northwest. Moscow and Tehran strongly support Syrian President Bashar al-Assad's government, while Turkey backs some rebel fighters in the region.