Nationwide violence killed 34 people on Sunday while civil servants west of Baghdad returned to work under tight security with Iraqi forces locked in a deadly two-week standoff with militants.

Gunmen and security forces clashed west and south of Baghdad, while bombings and shootings struck the capital and in northern Iraq, areas that have all borne the brunt of a months-long surge in bloodshed.

Armoured vehicles and tanks were meanwhile deployed at intersections in Ramadi, a former insurgent stronghold where authorities have wrested control of all but two neighbourhoods from militants as a crisis in surrounding Anbar province entered its 14th day.

Gunmen also hold Fallujah, another Anbar city and former militant bastion located 60 kilometres (37 miles) from Baghdad.

It is the first time militants have exercised such open control in major cities since the insurgency that followed the 2003 US-led invasion.

The worst of Sunday's violence, however, hit the capital and surrounding areas.

Car bombs in the predominantly Shiite area of Kadhimiyah and the confessionally mixed Allawi killed 14 people in total, while a roadside bomb in west Baghdad left another person dead.

Two militants were killed by security forces just south of Baghdad, while in Abu Ghraib, west of the capital, militants attacked Iraqi soldiers, after which at least one helicopter opened fire.

The violence killed at least eight people and wounded 17, but accounts of the incident differed.

One security official said all of the dead and wounded were civilians killed by helicopter fire, while a second said the casualties may also include militants, and that the toll was for the entire engagement.

And a medical official said both soldiers and civilians were killed.

Violence in Mosul, Tikrit and Tuz Khurmatu, all restive areas north of Baghdad, left nine others dead and dozens wounded, including two journalists injured by a magnetic "sticky bomb" attached to their car.

In Anbar, meanwhile, provincial council member Raja Barakat al-Aifan told AFP about 60 percent of government employees were back at work, after almost two weeks off due to the turmoil in the province.

Anbar governor Ahmed Khalaf al-Dulaimi had called for government employees to return to work on Sunday, the first day of the work week in much of the Arab world.

Also on Sunday, security forces backed by tanks battled militants in Albubali, said to have become a stronghold of Al-Qaeda-linked fighters between Ramadi and Fallujah, according to two policemen in the area.

Iraqi forces opened fire on a gathering of militants, killing a number of them, one of the policemen said, but it was unclear how many had died as the security forces had not yet managed to make it to the site of the gathering to collect the corpses.

And Sabah Noori, the spokesman for Iraq's Counter-Terrorism Service, said some of its members were missing in the area.

On Saturday, Fallujah residents who had fled the city began to return and most businesses had reopened.

But tribal leaders said a combination of anti-government tribesmen and fighters loyal to the Al-Qaeda-linked Islamic State of Iraq and the Levant (ISIL) still held the city.

Washington has piled pressure on Baghdad to focus on political reconciliation, in addition to ongoing military operations, but a US official has warned the crisis could take weeks to resolve.

The UN Security Council has voiced support for the government campaign to retake the two cities.

ISIL has been active in the Anbar fighting, but so have anti-government tribesmen.

At the same time, security forces have recruited their own tribal allies.

The army has for the most part stayed outside of Fallujah during the crisis, with analysts warning that any assault on the city would likely cause significant civilian casualties.

The Iraqi Red Crescent said it had provided humanitarian assistance to more than 8,000 families across Anbar but that upwards of 13,000 had fled Fallujah, while the UN special envoy has warned of a dire humanitarian situation.

Fighting erupted in the Ramadi area on December 30, when security forces cleared a year-old Sunni Arab protest camp.

The violence spread to Fallujah, and militants moved in and seized the city and parts of Ramadi after security forces withdrew.