Iraqi forces attacked a militant stronghold in crisis-hit Anbar province on Thursday, while authorities found 14 bullet-riddled bodies in scenes harkening back to the worst of the country's sectarian war.

The latest fighting, a day after nationwide attacks killed 73 people and gunmen made gains in Anbar, comes amid fears the country is sliding back into the worst of the brutal Sunni-Shiite conflict which killed tens of thousands in 2006 and 2007.

UN chief Ban Ki-moon and other diplomats have urged Baghdad to pursue political reconciliation with the disaffected Sunni Arab minority to end the weeks-long standoff in Anbar and the months-long surge in violence.

But with parliamentary elections looming in April, Prime Minister Nuri al-Maliki has ruled out dialogue with fighters who control parts of Anbar provincial capital Ramadi and all of Fallujah, just a short car journey from Baghdad.

Early Thursday, around 3,000 security personnel, comprised of units from the elite Golden Brigade linked to Maliki's office, and the interior ministry's Rapid Intervention Force, attacked an alleged militant camp in Albubali, a rural area between the two cities.

They were backed by tanks and aircraft, according to a senior police officer and a policeman.

"The main target is to take control of this area," the officer said.

They also aimed to recover the bodies of eight missing security personnel believed killed by militants.

Clashes were reported just west of Fallujah overnight, while mortar fire inside the city killed two people. It was unclear who was involved in the fighting, which has involved tribal allies on both sides.

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

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

The Al-Qaeda-linked Islamic State of Iraq and the Levant (ISIL) has been involved in the fighting along with anti-government tribesmen. The government has recruited its own allies among the province's powerful tribes.

The crisis marks the first time militants have exercised such open control in major cities since the height of the insurgency that followed the US-led invasion of 2003.

But while Iraqi officials have trumpeted security operations, which they say have led to the dismantling of training camps and bomb-making sites, the bloodshed has shown no sign of abating.

In the latest instance, the bodies of 14 men, all kidnapped earlier Thursday by men wearing army uniforms, were found shot dead in an orchard north of Baghdad, security and medical officials said.

The victims, taken from their homes in the predominantly Sunni Arab town of Mishahda, had all suffered gunshots to the head and chest, the officials said.

Among them were at least five members of one family.

At the peak of sectarian fighting in the wake of the 2003 US-led invasion, Sunni and Shiite militias regularly carried out tit-for-tat kidnappings and assassinations and left scores of corpses littering the streets.

At the time, many of the bodies were blindfolded and showed signs of torture.

Violence elsewhere in Baghdad, and north of the capital in Baquba and Tikrit, left four others dead.

The authorities have made some concessions aimed at placating the protesters and Sunnis in general, including freeing prisoners and raising the salaries of anti-Al-Qaeda Sahwa fighters.

But violence has persisted day by day, claiming nearly 600 lives already this month, according to an AFP tally.

Diplomats say the government is not doing enough to address Sunni anger over perceived mistreatment at the hands of the Shiite-led authorities.