Baghdad: Iraqi Kurdish forces on Sunday found and freed workers who had gone missing a day earlier when Daesh militants seized a small crude oil station near the northern city of Kirkuk, the provincial governor and a member of the provincial council said.

The Kurds retook the crude oil separation unit in Khabbaz on Saturday evening but had been unable to immediately determine the fate of the employees, whom they found in an underground room.

“All of them were rescued and they are all safe,” Kirkuk Governor Najm Al Deen Karim told Reuters by phone, denying reports that some of the workers had been taken hostage.

Earlier reports said 15 workers had gone missing, but provincial council member Ali Mahdi said the number could be as high as 25. Mahdi confirmed that the workers had all been freed.

One senior Kurdish commander was killed in Saturday’s attack, the most serious assault on Kirkuk since the summer.

Daesh militants seized at least four small oilfields when they overran large areas of northern Iraq last summer and began selling crude oil and gasoline to finance their operations.

Khabbaz is a small oilfield 20 kilometres southwest of Kirkuk with a maximum production capacity of 15,000 barrels per day (bpd). It was producing around 10,000 bpd before the attack.