US concerned by Russian military build-up in Syria

US Secretary of State John Kerry has expressed concern to his Russian counterpart over reports of "an imminent enhanced Russian military build-up" in Syria.

On Friday the New York Times reported that US officials believed Russia had sent a military advance team to Syria and was "taking other steps the United States fears may signal that President... Putin is planning to vastly expand his military support for [Syrian] President Bashar al-Assad".

Among the latest steps by Russia is the delivery of the temporary housing units and a portable air traffic control station to an airfield near the port city of Latakia, an Assad stronghold, the U.S. official said. The Russians have also filed military overflight requests with neighbouring countries, the U.S. official said. Russia has also dispatched a military advance team to Syria, the New York Times reported.

Kerry "made clear that if such reports were accurate, these actions could further escalate the conflict, lead to greater loss of innocent life, increase refugee flows and risk confrontation with the anti-ISIL coalition operating in Syria," the state department said.

Ealier today, clashes between rebels and Islamic State (IS) militants around the strategic Syrian town of Marea left 47 dead. 27 of the dead are IS combatants, said UK-based Syria Observatory for Human Rights, with the rest being from other anti-government groups. Last month it was reported IS may have used chemical weapons in an attack on Marea, which lies in an area that Turkey and the US plan to turn into a "safe zone," free of IS militants.

Medecins Sans Frontieres (MSF) said that on 21 August it had treated four members of a family who suffered from breathing difficulties and developed blisters after a mortar hit their home in Marea.

The Syrian American Medical Society has also reported receiving 50 patients showing symptoms of chemical exposure.