Turkey on Monday said it wanted international air support for its army's assault on the jihadist-held Syrian town of Al Bab where the military is facing tough resistance from Islamic State (IS) extremists.

Turkish forces have for weeks joined pro-Ankara Syrian rebels in fierce fighting for Al Bab, taking increasing casualties as they approach closer to the centre.

Turkey is part of the US-led coalition against IS jihadists in Syria and lets Western war planes use its Incirlik air base as a hub for air raids.  

"As for our operations in Al Bab, the international coalition should assume its responsibilities, especially where air support is concerned," presidential spokesman Ibrahim Kalin said in televised comments in Ankara.

"The weather conditions can sometimes entail delays," Kalin acknowledged. "But the absence of air support when there is no valid reason is unacceptable," he added.

The US and its allies have been conducting their own air strikes against IS targets in Syria but there have been no reports of them specifically aiding the Turkish operation.

Turkey at the weekend deployed more tanks and artillery to the border and also has sent 500 elite commandos to Al Bab in readiness for a final fight for the town, reports said.

A Britain-based monitoring group has accused Turkey of killing 88 civilians in air strikes on Al-Bab. However the army has unequivocally denied such claims.

Thirty-six Turkish soldiers have died so far in the operation inside Syria -- dubbed Euphrates Shield -- since it was launched on August 24.

Islamic State jihadists last week circulated a video purportedly showing two Turkish soldiers captured by the extremists in Syria being burned alive.

The authenticity of the video cannot be confirmed and Turkey's leadership has made no mention of the images.

Turkey's Defence Minister Fikri Isik has said three Turkish soldiers are being held by IS, without giving further detail. The issue was evoked at Kalin's televised news conference but the spokesman did not give any comment.

Users in Turkey had reported severe problems with social media after the video emerged. However by Monday access to Twitter was fully restored after three days of disruption.

Source: AFP