BEIRUT - Britain is providing aerial surveillance to help a newly launched offensive against the Syrian city of Raqqa, the de facto capital of the Islamic State group's self-described caliphate.

Defense Secretary Michael Fallon says the Royal Air Force "will support the Raqqa operation as it develops." He said the "sophisticated surveillance effort" would give the coalition a vital edge in Syria.

A Syrian Kurdish-led force which is backed by U.S.-led air power announced an operation to retake Raqqa earlier Sunday.

Fallon also said UK strikes are "making a difference" in the sustained assault against IS in the northern Iraqi city of Mosul, where Iraqi forces launched a major operation last month to drive out the extremists.

The two cities are the largest controlled by the extremist group.