More than 50 air strikes in recent days by coalition aircraft "have resulted in allowing those (Kurdish) forces to manuever and regain approximately 100 square kilometers (38 square miles) of ground" near Sinjar, Lieutenant General James Terry, head of the US-led campaign against the IS group, told reporters.

Kurdish peshmerga forces said earlier they had captured several villages and were rolling back the IS militants around Sinjar in the country's northwest.

The capture of Sinjar by IS jihadists in early August and the plight of the mostly Yazidi minority population there was cited by President Barack Obama as one of the reasons for US military intervention.

US and allied aircraft have carried out 1,361 raids against the IS group since bombing began on August 8, Terry said.

The advance of the IS militants had been halted and the group was having difficulty moving and communicating as a result of the air campaign, he said.

"I think we've made significant progress in halting that progress (by IS)," he said.