Syria crisis: Turkey says coalition to launch 'comprehensive battle' on Islamic State

U.S. aircraft and drones are arriving at Turkish air bases and a comprehensive battle against Islamic State militants will be launched soon, Turkish Foreign Minister Mevlut Cavusoglu said on Wednesday.

• NATO vows solidarity with Turkey over ISIS threat but urges peace with Kurds
• U.S., Turkey working to establish ISIS-free zone in northern Syria
• Syria crisis: Turkish fighter jets strike ISIS targets across border

Turkey formally approved the use of its air bases by U.S. and coalition aircraft late last month, a major change in policy after years of reluctance in taking a front-line role against the Islamist fighters in northern Syria.

"As part of our agreement with the U.S. we have made progress regarding the opening up of our bases, particularly Incirlik," Cavusoglu told state broadcaster TRT, referring to a major air base near the southern city of Adana.

"We're seeing that manned and unmanned American planes are arriving and soon we will launch a comprehensive battle against Islamic State all together," he said during a trip to Malaysia.

Turkey and the United States have been working on plans to provide air cover for a group of U.S.-trained Syrian rebels and jointly sweep Islamic State fighters from a strip of northern Syria stretching about 80 kilometres along the Turkish border.

Diplomats familiar with the plans say cutting off Islamic State's access to the border, over which foreign fighters and supplies have flowed, could be a game-changer in the fight against the insurgents.

But there are major challenges.

Washington said on Tuesday it had indications some of the rebels trained by its military were captured by fighters from al Qaeda's Syria wing, Nusra Front, underscoring the vulnerability of a group thought to number less than 60 who only deployed to the battlefield in recent weeks.

Islamic State has seized large parts of Syria and neighbouring Iraq in its drive to create an Islamic caliphate.