Islamic State militants overran one of the last remaining districts held by government forces in the Iraqi city of Ramadi yesterday and besieged a key army base on the edge of the western provincial capital, security sources said.

The militants seized most of Ramadi on Friday, planting their black flag on the local government headquarters in the centre of the city, but a contingent of Iraqi special forces was holding out in the Malaab neighbourhood.

Smoke rising after a bomb attack by Islamic State militants in the city of Ramadi yesterday. Photos: Reuters

Those forces retreated yesterday to an area east of the city after suffering heavy casualties, security sources said, bringing Ramadi to the brink of falling to Islamic State.

It would be the first major urban centre to be seized by the insurgents in Iraq since security forces and paramilitary groups began pushing them back last year.

Anbar provincial council member Athal Fahdawi described the situation in Ramadi as “total collapse” and said local officials had voted in favour of the deployment of Shi’ite paramilitaries to the Sunni heartland.

Shi’ite paramilitaries have played a leading role in reversing Islamic State gains elsewhere in Iraq, but have so far been kept on the sidelines in Anbar due to concerns about inflaming sectarian violence.

The insurgents were closing in on the Anbar Operations Command to the west and a military officer inside the army base said it was too late to send reinforcements, pleading for help from Iraqi Prime Minister Haider al-Abadi.

Fights are in almost every street, things are sliding out of control

“We are now surrounded inside the Operations Command by Daesh, and mortars are raining down,” said the officer. Daesh is an Arabic acronym for Islamic State.

“Daesh fighters are in almost every street. It’s a chaotic situation and things are sliding out of control. Ramadi is falling into the hands of Daesh,” the officer said.

Islamic State, an offshoot of al-Qaeda, controls large parts of Iraq and Syria in a self-proclaimed caliphate. It has massacred religious minorities and slaughtered Western and Arab hostages.

Ramadi is the capital of Anbar, Iraq’s largest province, and one of just a few towns and cities to have remained under government control in the vast desert terrain, which borders Saudi Arabia, Syria and Jordan.