Five Turkish soldiers were killed and five others were wounded on Monday as a result of "intense" shelling by Syrian government forces in Syria's northern Idlib province, according to the Turkish defence ministry.

The ministry statement said Turkish artillery immediately responded to the attack, destroying targets.

Turkey has sent major reinforcements to Syria's northwestern Idlib region where the attack occurred, as Ankara tries to stem rapid advances by Syrian government forces.

A rebel commander said the insurgents launched a military operation on Monday against the Syrian army near Saraqeb with the help of Turkish artillery, with witnesses also reporting Turkish shelling of Syrian military positions in the region.

“Saraqeb is a town on the highway between Syrian capital Damascus and [the Syrian economic hub] Aleppo. Syria government troops took it last week. Today’s attack was obviously an attempt by pro-Turkish forces to reverse that gain,” said FRANCE 24’s Jasper Mortimer, reporting from Ankara.

Observation posts under Astana accords

Syrian President Bashar al-Assad's forces, backed by Russian air cover, have been advancing into the last rebel-held areas of Idlib and the nearby Aleppo countryside, seizing dozens of towns and sparking a large-scale humanitarian crisis with some 600,000 people fleeing from their homes towards safer areas near the border with Turkey.

Most of the displaced are living in open-air shelters and temporary homes in freezing winter conditions close to the border. Half of the displaced are believed to be children.

The fighting led to the collapse of a fragile cease-fire that was brokered between Turkey, Russia and Iran under the 2018 Astana accords. Russia and Turkey back opposing sides in the Syrian war: Turkey supports the Syrian rebels, while Russia has heavily backed the Syrian government's offensive.

"Turkey is running 12 observation posts that were set up with Russia and Iranian approval under the Astana accord with the purpose of quietening the fighting in that province between the rebels opposed to President Bashar al-Assad and Assad’s own forces. For a time, these observation posts did succeed in quietening the civil war in that province. But in the last few months Assad's forces have launched an attack to drive the rebels out of Idlib," explained Mortimer.

Russian delegation in Ankara for talks

The latest attack came as a Russian delegation arrived in the Turkish capital of Ankara for a second round of talks to discuss the rising tensions in Idlib.

Turkish Foreign Minister Mevlut Cavusoglu said Turkish and Russian delegations exchanged proposals over the situation in Idlib during a first meeting in Ankara on Saturday. On Monday, the Russian team returned to Ankara from a visit to Jordan, for further discussions, he said.

"If a compromise had been reached there would have been no need for today's meeting," Cavusoglu told reporters. He said the Turkish and Russian leaders could step in if no compromise is reached.

Syria's military has vowed to keep up its campaign.

Deadly car bombing in Afrin

Meanwhile, a car bomb exploded Monday in a Syrian town controlled by Turkey-backed opposition fighters, killing at least four people and wounding 15 others, Turkey's state-run Anadolu Agency reported.

The attack was the latest in a series of explosions in Turkish-controlled regions that have killed and wounded scores of people. Turkey has blamed the attacks on the Syrian Kurdish militia, known as the People's Protection Units.

The bomb went off on a main street in the town of Afrin, which Turkey took control of following a military incursion in 2018, Anadolu reported. It said some of the wounded were in serious condition, adding that the death toll was likely to rise.

The Turkish offensive aimed at pushing Kurdish fighters away from the border. Those Kurdish fighters had been key U.S. allies in the fight against the Islamic State group. Turkey considers the Syrian Kurdish fighters terrorists linked to a Kurdish insurgency within Turkey.