Iraq has battled a militant assault on the city of Ramadi while the Kurds have claimed disputed oilfields, another blow to efforts to forge a united front against a jihadist-led onslaught.

The militant push to take the capital of Anbar province comes two days before a planned parliamentary session to revive flagging efforts to replace the caretaker government in power since April elections.

Sunni militants have captured areas west of Ramadi since the fighting began on Thursday afternoon, killing 11 police, bombing a police station and capturing another, an officer and a doctor said.

The officer, a police lieutenant colonel, said the insurgents were attempting to “storm Ramadi from the western side”.

The fall of the city, where anti-government fighters have held shifting areas since early this year, would be a major advance for the jihadist-led militants who have overrun large areas of five provinces, including parts of Anbar, since June 9.

It could increase the threat to the capital by solidifying militant positions in Anbar and breaking the isolation of insurgent-held Fallujah, which lies only 60 kilometres west of Baghdad.

As the battle for Ramadi raged, Iraq’s autonomous Kurdish region claimed control of several disputed northern oilfields.

“Members of the Kurdistan Regional Government and Kirkuk Oil Protection Forces moved to secure the oilfields of Bai Hassan and the Makhmour area,” the region’s government said.

“Production at the new fields under KRG control will be used primarily to fill the shortage of refined products in the domestic market,” it said, adding that staff from the federal North Oil Company could either cooperate with new management or leave.

The move enraged the Baghdad government, which labelled it “irresponsible behaviour which violates the constitution and the national wealth, and disregards the federal authorities and threatens national unity”.

The oilfield seizures come after Kurdish peshmerga fighters moved into stretches of disputed northern areas vacated by Iraqi forces during the initial militant offensive last month, and regional president Massud Barzani has said they will stay there.