MOSUL: A pre-dawn attack on an army encampment guarding an oil pipeline in northern Iraq killed 15 soldiers on Tuesday as authorities grapple with near-daily attacks and running battles with militants.

The latest bloodshed comes with unrest at its worst in Iraq in nearly six years, and has fuelled fears that, with elections due in April, the country is on the brink of slipping back into the sectarian violence that plagued it in the years following the 2003 US-led invasion.

Foreign leaders have urged the Shia-led government to do more to reach out to the disaffected Sunni Arab minority but Prime Minister Nuri al-Maliki has taken a hard line and trumpeted wide-ranging operations against militants.

Insurgents regularly mount deadly attacks, with gunmen early Tuesday morning entering the army encampment in Nineveh province and killing all 15 soldiers at the site before fleeing the scene, according to a police officer and a morgue official.

The encampment was set up to guard an oil pipeline near Hamam al-Alil, a town that like the rest of the surrounding province is regularly hit by militant attacks.

The style of the attack, targeting a station housing security forces guarding an important piece of infrastructure, mirrored that of a similar shooting in the northern town of Tuz Khurmatu on Sunday in which six policemen were killed.

In that instance, the policemen were forced to pray in front of their attackers, who wanted to establish that the police were Shia Muslims before killing them.

No group has claimed responsibility for most of the bloodshed in recent months, but Sunni militants including the Islamic State of Iraq and the Levant, a powerful jihadist group, often target Iraq's security forces and have been blamed by Baghdad.

The latest unrest is part of a protracted surge in violence that has sparked concerns Iraq is slipping back into the brutal fighting of 2006 and 2007, when Sunni and Shia militias carried out near-daily sectarian attacks and made the country virtually ungovernable.

Government figures show that more than 1,000 people were killed last month alone.

On Monday, a car bomb targeting security forces carrying out raids in Khaldiyah, a conflict-hit area of Anbar province, killed nine policemen, Lieutenant Colonel Hamad al-Tiktakhi said.

Soldiers and police in Anbar have allied with tribal fighters to try to retake parts of the mainly Sunni desert region bordering Syria that have been out of Baghdad's control for more than a month.

Anbar's governor over the weekend gave militants controlling Fallujah one week to surrender, as government forces made steady progress in nearby Ramadi as part of efforts to end the crisis.

Pro-government forces have largely stayed out of Fallujah, fearing that an incursion could spark a drawn-out urban conflict with high numbers of casualties.

The city was a bastion of the Sunni insurgency following the US-led invasion, and American troops there fought some of their costliest battles since the Vietnam War.

The Anbar stand-off has prompted more than 140,000 people to flee their homes, the UN refugee agency said last month, calling it the worst displacement in Iraq since the peak of sectarian fighting between 2006 and 2008.