The Isis militant group is reported to have secured its biggest military victory in almost a year, capturing one of the last remaining districts of the major city of Ramadi.

Iraqi military forces retreated from the city on Sunday, despite a desperate plea broadcast on state TV from the Prime Minister, Haider al-Abadi, begging them not to abandon their positions.

There are fears that the fall of Ramadi, the capital of Iraq’s biggest province Anbar, will establish a new stronghold for the jihadist group, and quickly be followed by new mass executions and slaughters as the last remaining government forces are wiped out.

Earlier, al-Abadi had ordered Shia militia in surrounding provinces to prepare to go into Anbar in a last-ditch effort to save the province. That was despite concerns from those within the Sunni-dominated region that it could spark a sectarian bloodbath.

According to The Associated Press it was not immediately clear on Sunday evening whether any of the city remained in government hands.

Iraqi security forces withdraw from the Anbar state capital, Ramadi, in defeat on Sunday, 17 May (AP)

Ramadi’s loss would make it the first major city to be taken by insurgents since Iraqi forces backed by a US-led coalition of air forces began pushing back against the Isis advance.

Those coalition air strikes continued throughout the weekend, according to a statement from the Combined Joint Task Force, including seven around Ramadi.

The US military said its strikes had targeted tactical units, a facility producing improvised explosive devices, and other buildings, but it appears to have failed to keep Isis out of the Anbar capital.

Fall of Ramadi Show all 17 1 /17 Fall of Ramadi Fall of Ramadi Fall of Ramadi A displaced Iraqi Sunni man pushes an elderly woman in a wheelchair on the outskirts of Baghdad. Reuters Fall of Ramadi Fall of Ramadi An Iraqi family, who fled the city of Ramadi after it was seized by Islamic State (IS) group militants, gathers inside a tent at a camp housing displaced families. AFP Fall of Ramadi Fall of Ramadi Displaced Iraqis from Ramadi. AP Fall of Ramadi Fall of Ramadi Iraqi fighters of the Shiite militia Asaib Ahl al-Haq (The League of the Righteous) stand guard outside their headquarters AFP Fall of Ramadi Fall of Ramadi Iraqis fleeing from their hometown of Ramadi walk on a street near the Bzebiz bridge, 65 kilometers (40 miles) west of Baghdad. AP Fall of Ramadi Fall of Ramadi Iraqi Sunni tribal leaders demand Prime Minister Haider al-Abadi to send forces to protect their city and regain Ramadi shortly after Iraqi security forces withdraw from the city. AFP Fall of Ramadi Fall of Ramadi Displaced Iraqis from Ramadi rest before crossing the Bzebiz bridge after spending the night walking towards Baghdad. AP Fall of Ramadi Fall of Ramadi Ramadi, after fighting on Friday, was one of the army’s few strongholds Reuters Fall of Ramadi Fall of Ramadi Iraqi security forces withdraw from the Anbar state capital, Ramadi, in defeat on Sunday, 17 May (AP) AP Fall of Ramadi Fall of Ramadi Iraqis fleeing from their hometown of Ramadi walk on a street near the Bzebiz bridge, 65 kilometers (40 miles) west of Baghdad AP Fall of Ramadi Fall of Ramadi 130,000 remaining inhabitants of Ramadi, an overwhelmingly Sunni city, have fled the fighting (AP) AP Fall of Ramadi Fall of Ramadi Thousands of civilians fled the Isis advance in Ramadi AP Fall of Ramadi Fall of Ramadi Iraq security forces were seen fleeing from Ramadi, the capital of Iraq's Anbar province AP Fall of Ramadi Fall of Ramadi Civilian belongings can be seen in an abandoned truck during fighting in Ramadi Reuters Fall of Ramadi Fall of Ramadi Isis led its renewed assault on Ramadi with suicide car bombs on Friday Reuters Fall of Ramadi Fall of Ramadi The last remaining Iraqi security forces defending their headquarters against Isis in the eastern part of Ramadi on 14 May Reuters Fall of Ramadi Fall of Ramadi Civilians fled Ramadi as Isis advanced earlier in May. Reuters

US officials have sought to play down the importance of Ramadi since it was threatened by Isis in recent weeks. The chair of the joint chiefs of staff said in April that the city was “not symbolic in any way”.

But writing in a blog post for aj-Jazeera, security correspondent Imran Khan said the home to 500,000 people was hugely significant as a melting-pot for anti-government Sunni dissent.

The last time Isis took a city of an equivalent size in Iraq was the fall of Mosul in June 2014 – now the main Iraqi hub for the group.