Syria Rebels Reenter Key Idlib Crossroads Town: AFP

Syrian rebels reentered the key northwestern crossroads town of Saraqeb lost to government forces earlier this month but fierce fighting raged on in its outskirts Thursday, an AFP correspondent reported.

The counterattack by jihadist fighters and their rebel allies cuts the main Damascus-Aleppo highway, which passes through the town, and reverses one of the principal gains of the devastating offensive the government launched against the country's last major rebel bastion in Idlib province in December.

State news agency SANA acknowledged that there were "fierce clashes" between the army and "terrorist groups on the Saraqeb front".

An AFP correspondent accompanied the rebels into Saraqeb, where he found a ghost town of bombed out buildings deserted by its inhabitants.

The correspondent saw rebel fighters deploy inside the town in large numbers, where they come under attack from government forces on the outskirts as well as from the air.

The Britain-based Syrian Observatory for Human Rights said that the air strikes were carried out by government ally Russia, which has come under heavy Western criticism for the high civilian death toll from its bombing campaign.

State media accused the "terrorists" of launching car bombings and other suicide attacks against government forces attempting to retake the town which they had held since February 8.

It said that the army had inflicted heavy losses on the attackers, despite the military support it said they had received from neighbouring Turkey.

Some 950,0000 civilians have fled the government offensive, raising fears in Ankara of a new mass influx of refugees.

Turkey already hosts the world's largest number of Syrian refugees with around 3.6 million people placing an increasingly unpopular burden on public services.

The Turkish defence ministry said on Thursday that two of its soldiers had been killed by government fire in Idlib, taking its losses this month alone to 19.

Turkey, which supports several rebel groups in the Idlib region, immediately responded to the attack by hitting Syrian "regime targets", the ministry said on Twitter.

President Recep Tayyip Erdogan vowed on Wednesday that Ankara would not take the "smallest step back" in the standoff with Damascus and Moscow over Idlib.

He warned the Syrian government to "stop its attacks as soon as possible" and to pull back by the end of the month.

Under a deal with Russia intended to bring calm to Idlib, Turkey has 12 observation posts in the region but several have come under fire from Assad forces.

The United Nations has warned repeatedly that the fighting in Idlib has the potential to create the most serious humanitarian crisis since the start of the civil war in 2011.