The jihadist group Islamic State in Iraq and Syria (Isis) has lost control of its remaining oil field assets in Iraq after being driven out from an area near Kirkuk last week, according to reports.

US-backed Iraqi forces ousted Isis from the Shirqat field on 22 September, after the group was driven out of the Qayyara field south of Mosul in August.

Isis has sold oil from assets seized in Iraq and Syria to fund its expansion across large areas of the two countries. Iraqi forces have not yet recaptured the Najma oil field, but Isis does not have access to its producing wells.

“Najma has yet to be liberated because some sites are in the conflict zone. The reality is that it is extremely difficult to extract and smuggle oil while our forces are advancing towards Mosul…” oil ministry spokesman Asim Jihad was quoted by UK news agency Reuters as saying.

Following the Isis offensive in northern and western Iraq in the summer of 2014, the militant group and Iraqi security forces fought over the country’s largest refinery at Baiji before Baghdad regained full control in October 2015.

Isis still controls producing oil wells in Syrian territory.