IS hit on several fronts by Syrian and Russian warplanes, rebel fighters

US-backed Syrian rebels advancing on Islamic State group fighters in the strategic northern town of Manbij have progressed to within five kilometers of the jihadist bastion, a monitor said on Sunday.

Supported by airstrikes by the US-led coalition battling IS in Syria and Iraq, the Syrian Democratic Forces alliance of Kurdish and Arab militias launched an assault last week on Manbij.

"The Syrian Democratic Forces are now within about five kilometers of the strategic city of Manbij," said the Syrian Observatory for Human Rights, a Britain-based monitoring group.