Syrian Kurds say militant group shoring up de facto capital Raqqa

Islamic State fighters appear to be shoring up their defences around their Syrian stronghold Raqqa city after losing ground to Kurdish-led forces this week, a spokesman for the Kurdish YPG militia said on Wednesday.

A Kurdish-led advance deep into the heart of Islamic State territory is reversing the momentum of the militants, who seized major towns in both Syria and Iraq last month.

Kurds and their Syrian rebel allies came within 50 km (30 miles) of Raqqa city, Islamic State's de facto capital, from which it rules over a self-declared caliphate across large areas of Syria and Iraq.

On Wednesday YPG spokesman Redur Xelil said in an online message the Kurds had received information that Islamic State had "begun digging trenches in the vicinity of Raqqa to improve their defences" following the Kurdish advances.

The YPG said on Tuesday it was not yet planning an assault on Raqqa and the Syrian Observatory for Human Rights monitoring group has said the operations were aimed at seizing control of an east-west highway which links the city of Aleppo with the northeastern province of Hasaka.

On Tuesday the Kurdish-led forces took control of Ain Issa town as Islamic State withdrew, after capturing the nearby Liwa-93 military base, a strategic site which Islamic State had captured last year from government forces.

The YPG fighters have emerged as the most credible ally of the U.S.-led campaign on the ground in Syria against Islamic State and the YPG says there is close coordination.