Al-Qosh, Iraq: Iraqi Kurds backed by US warplanes have retaken the country's largest dam from jihadists, as Sunni tribesmen and security forces continue to fight the militants west of Baghdad.

The recapture of Mosul dam marks the biggest prize clawed back from Islamic State (or IS, also known as ISIL) jihadists since they launched a northern offensive in early June when they swept Iraqi security forces aside.

A Kurdish Peshmerga fighter prepares his weapon at his combat position near the Mosul Dam. Credit:AP

IS militants, who have declared a "caliphate" straddling vast areas of Iraq and Syria, also came under air attack in their Syrian stronghold of Raqa on Sunday, a monitoring group said.

Syria's air force carried out 16 raids on the city of Raqqa and several more on the town of Tabqa in Raqqa province, killing at least 31 jihadists and eight civilians, said the Syrian Observatory for Human Rights.