IS militants re-take villages south of Syria's Manbij

IS militants re-took three villages south of the besieged city after launching a surprise assault against the Kurdish-led Syrian Democratic Forces [SDF], killing at least 28 fighters.

The militants encircled the besieged city with improvised remote bombs, to prevent SDF from advancing.

"The whole city is booby-trapped," Sharfan Darwish, SDF spokesman, told Reuters. "After 20 days of the campaign, we have yet to storm the city."

The SDF, comprised of a Kurdish-Arab alliance, had managed to press its way to the western entrance of Manbij city for the first time since the offensive took off on 31 May.

On Saturday, they had come two kilometres from the city centre before pulling back.

Figures from the past week showed at least 223 IS fighters and 28 SDF troops had been killed - as well as 41 civilians in coalition air raids - since the alliance's offensive on Manbij began, according to the UK-based Syrian Observatory for Human Rights.

Manbij lies at the heart of the last stretch of IS-controlled territory along Turkey's border.

The siege has severed a key supply route for IS fighters, money and weapons from the Turkish border to the group's de facto Syrian capital of Raqqa city.

Syria's war has killed 280,000 people and displaced millions since it erupted with the brutal repression of anti-government protests in 2011.

IS has come under attack on several fronts since declaring a cross-border "caliphate" in Syria and Iraq in 2014.