Many of the soldiers had been shot at close range. Some of the dead had their hands tied behind their backs, a medical worker told the AP news agency.

Insurgents in Sunni-dominated parts of northern and western Iraq have been fighting security forces under the command of the Shia-led government.

Violence has peaked again since the sectarian conflict of the last decade.

The UN says more than 8,000 people were killed in Iraq last year, the highest figure since 2007.

The government has blamed the rising bloodshed on Sunni militants, linking it to the conflict in neighbouring Syria.

But many analysts and diplomats say the government, led by Prime Minister Nuri al-Maliki, has contributed to the unrest by alienating the Sunni minority.

Iraq held a parliamentary election earlier this month. The result has not yet been announced.

The attack near Mosul took place on Saturday night, according to police officers quoted by AP.

However, a senior army officer told the AFP news agency that the attack had happened earlier in the week.

Officials also offered differing accounts of how the soldiers died, with some saying that they had been executed after being kidnapped from the base.

A police major, interviewed by AFP, contradicted reports that the slain men had their hands tied.

The soldiers had been responsible for guarding a nearby oil pipeline.

On Saturday, 11 people were reported killed in the western city of Falluja. Medical officials said the deaths were caused by government shelling and by an explosion in a car.

Security forces have been trying to retake the city from militants based there.