Turkey vows to press Syria offensive in spite of warning from pro-Assad forces

Turkey said on Wednesday it will pursue its military offensive in Syria until the Islamic State (IS) is driven from the town of al-Bab, in spite of a warning from forces allied with Syrian President Bashar al-Assad and a helicopter attack on rebel forces that it backs.

Turkey's incursion into Syria, launched two months ago to drive IS militants from its border and prevent Kurdish fighters from gaining ground in their wake, has complicated an already messy battlefield in northern Syria.

As the Turkey-backed rebels push south towards al-Bab, an IS-held town 35km northeast of Aleppo, they risk confrontation with both Kurdish and pro-Assad forces, whose frontlines are close by.

The field commander of the forces allied to the Syrian leader - which include the Lebanese group Hezbollah, Iraqi militias and the Iranian Revolutionary Guards - warned Turkey that any advance towards their positions north and east of Aleppo would be met "decisively and with force".

The commander, who was not identified by name, nationality or affiliation, made the comments during a tour of frontlines north of Aleppo in a written statement sent to Reuters. It came a day after what the Turkish military said was a barrel bomb attack on rebels it backs by a Syrian helicopter near the border town of Dabiq.

It was the first time a direct clash between Syrian forces and the Turkey-backed rebels has been announced. Two rebels were killed and five wounded, the Turkish army said.

The Syrian government said last week that the presence of Turkish troops on Syrian soil was a "dangerous escalation and flagrant breach of Syria's sovereignty". It also warned it would shoot down any Turkish warplanes entering Syrian air space.

"This kind of attack will not stop our fight against Daesh (IS)," Turkish Foreign Minister Mevlut Cavusoglu told a news conference in the capital Ankara.

"This operation will continue until al-Bab. The operation needs to continue, and it will," he said.

President Tayyip Erdogan said Turkey's military operations in Syria aim to secure al-Bab and the town of Manbij, which a group of US-backed Kurdish and Arab fighters seized from IS in August, but were not intended to stretch to Aleppo.

"Let's make a joint fight against terrorist organisations. But Aleppo belongs to the people of Aleppo ... making calculations over Aleppo would not be right," he said in a speech in Ankara.

US President Barack Obama, in a telephone call with Erdogan on Wednesday, recognized Turkey's contributions to the fight against IS, especially is supporting Syrian forces that have cleared the militants from the Turkish border, the White House said in a statement.

Obama "noted the need for close coordination" between the two countries to apply sustained pressure on IS in Syria, the statement said.

The two leaders also agreed on the importance of denying Kurdish PKK militants a safe haven in northern Iraq, it added.