Syrian Democratic Forces capture villages from IS

US-backed Kurdish-Arab forces have started their offensive on Raqqa in eastern Syria, the Islamic State group's self-declared capital, winning villages and hamlets from the militants.

US-led coalition war planes launched 16 air raids in northern Syria, hitting the Ein al-Issa area, north of Raqqa, destroying six IS fighting positions, five vehicles and two vehicles rigged with explosives.

Syrian Democratic Forces commanders declared the start of Operation Wrath of the Euphrates on Sunday from Ain al-Issa, some 50 kilometres (30 miles) north of Raqqa. 

The operation involving some 30,000 mostly Kurdish fighters has seen early successes with Syrian Democratic Forces advancing on three fronts.

Land has been taken from Ain al-Issa and Tal Abyad north of Raqqa, and from the village of Makman to the east.

The Syrian Democratic Forces said ten villages and several hamlets had been taken from IS.

The People's Protection Units (YPG) which forms the bulk of the Syrian Democratic Forces denied an IS claim that one of its militants had killed 14 Kurdish fighters.

Central to the campaign will be the input of US-led coalition advisers and air power.

The coalition is said to have provided hundreds of US special forces to work with the Iraqi army and Kurdish fighters in Syria and Iraq.

An AFP correspondent saw at least one soldier who had US markings on his helmet with SDF fighters in Ain al-Issa.

The SDF said the alliance had received new weapons from the coalition for the Raqqa battle, including anti-tank missiles.

Another SDF source said 50 US military advisers would be involved in the operation, particularly to guide air strikes.

The SDF have agreed with the US that no Turkish troops or its allies will be involved in the operation, despite the presence of Syrian rebels backed by Ankara close by.

In Jordan, however, President Barack Obama's envoy Brett McGurk said Washington was in "close contact" with Ankara over the assault.