Two Turkish soldiers are missing in Syria, the army said late on Tuesday, as the military presses an operation to expel Islamic State (IS) jihadists from the border area.

"Contact was lost with two of our soldiers," a military statement said.

Earlier the IS-linked Amaq news agency claimed that the jihadist group had taken the pair hostage in northern Syria.

The Turkish army said searches were under way for the missing men after contact was lost at around 1230 GMT. They did not say where the two soldiers were at the time.

The Syrian Observatory for Human Rights said they disappeared in the Aldana area west of Al Bab in Aleppo province.

But it could not confirm whether or not they had been kidnapped.

The Turkish army embarked on an ambitious operation inside Syria in August to root out IS jihadists from the border area and to halt the advance of Syrian Kurdish militia forces.

Rebels have since then captured IS strongholds of Jarabulus, Al Rai and liberated the symbolically important town of Dabiq, without much resistance.

Backed by Turkey, they are now pressing to take Al Bab, deeper inside Syria, from the jihadist group.

On Sunday, the Turkish army said 22 Syrian rebels were hit by an IS gas attack in northern Syria.

It was the first time Ankara has accused the group of chemical warfare.