The Iraqi army has withdrawn from its last base in the city of Heet, in Anbar province, following weeks of fighting with the Islamic State in Syria and the Levant (ISIL), leaving the armed group in full control, security sources say.

Hundreds of troops were pulled out of the base and relocated to help protect the Asad airbase, the AFP news agency quoted a police colonel in the provincial capital of Ramadi as saying on Monday.

"Our military leaders argued that instead of leaving those forces exposed to attacks by ISIL, they would be best used to shore up the defence of Asad airbase," he said.

"Hit [Heet] is now 100 percent under ISIL control."

Asad, northwest of Heet, is one of the last still under government control in the western province. It is surrounded by desert and a tougher target for ISIL fighters.

Other security officials said military aircraft picked up senior officers from the Heet base, and the rest of the force drove in a convoy to Asad.

An Iraqi officer and Sunni militia fighters told the Reuters news agency that ISIL looted three armoured vehicles and at least five tanks, and then set the camp ablaze.

Series of setbacks

Government forces have suffered a series of setbacks in Anbar in recent weeks, and officials have warned that their grip on the capital Ramadi was increasingly tenuous.

Al Jazeera's Imran Khan, reporting from Baghdad, said that ISIL's takeover puts nearby towns including Amiri under threat.

"Amiri is a very key town, that is where the main supply line from Anbar province into Baghdad and the rest of the south of the country goes from," he said.

Up to 180,000 people have been displaced by fighting in and around Hit, the UN office for humanitarian affairs said on Monday.

The city had been home to 100,000 people who had fled other areas of Iraq which had fallen to ISIL, it said.

ISIL is also suspected of carrying out three bombings on Monday in mainly Shia neighbourhoods in Baghdad, killing dozens of people.

There have been a number of similar attacks in Baghdad in the past week, with suicide blasts on Sunday alone killing at least 45 people.

During a visit to Baghdad on Monday, Phillip Hammond, UK foreign minister, said ISIL would only be defeated by "heavy work on the ground" by Iraqi forces.

''We've always understood that the air campaign alone was not going to be decisive in turning the tide against ISIL but it has halted the ISIL advance ... and it is degrading their military capabilities and their economic strength," he said.

"The heavy work on the ground is going to have been done by Iraqi forces and it is going to have been done by the Sunni communities in the areas that ISIL occupies.''