US jets have struck jihadist positions in northern Iraq, in what the federal and Kurdish governments vowed would allow them to start clawing back areas lost in two months of conflict.

President Barack Obama’s order for the first air strikes on Iraq since he put an end to US occupation in 2011 came on Friday after Islamic State (IS) militants made massive gains on the ground, seizing a dam and forcing a mass exodus of religious minorities.

The Pentagon said US forces bombed an artillery position after fire against Kurdish regional government forces defending their capital Arbil.

In a second wave hours later, a drone destroyed a mortar position and jets hit a seven-vehicle IS convoy with eight laser-guided bombs.

The US operation began with air drops of food and water for thousands of people hiding from the Sunni extremist militants in a barren northern mountain range.

Obama accused the IS, which calls Yazidis “devil-worshippers”, of attempting “the systematic destruction of the entire people, which would constitute genocide”.

The UN said it was “urgently preparing a humanitarian corridor”.

Obama suggested the strikes would be “limited” in scope, but “has not laid a specific end date”, White House spokesman Josh Earnest told reporters, while insisting a “prolonged military conflict that includes US involvement is not on the table”.

Iraq’s military chief of staff said he expected to see his forces and the peshmerga reclaim large tracts of land “in the coming hours”.

He said he thought the US air strikes would extend to other towns controlled by IS but he did not say which ones.

The Kurdish presidency’s chief of staff, Fuad Hussein, said at a news conference in Arbil late Friday that 150 peshmerga had been killed in two months of fighting a long a front stretching more than 1000 kilometres.

He said the US strikes would allow routed Kurdish forces to retake the initiative and carry out a three-phase plan: regroup, redeploy in lost areas and assist the return of displaced populations.