The IS group took over large swathes of Iraq and Syria in 2014, declaring itself a new "caliphate" for Muslims, before Baghdad declared victory after a grinding campaign in late 2017.

But a low-level insurgency by the extremist Sunni group has persisted, flaring up at various points, especially in rural areas north of Baghdad around the city of Kirkuk, and in the eastern provinces of Diyala and Salaheddin.

"Eleven soldiers... have been killed during an attack carried out by the Islamic State... targeting a base of the army" in Diyala province, a senior military official based there said, on condition of anonymity.

The attack took place "around 2:30am (2330 GMT) against a base in the Hawi al-Azim area," the source added.

Diyala province governor Muthanna al-Tamimi confirmed the death toll, according to the Iraqi News Agency.

But he also hit out at the Iraqi army, alleging they were caught unprepared.

"The base is fortified. There is a thermal camera, night vision goggles and a concrete watch-tower," he said.

"The terrorists exploited the cold and the negligence of the soldiers," he alleged, adding that the attackers then escaped to the neighbouring province of Salaheddin.

Since the Iraqi government declared victory four years ago, the jihadists have waged an insurgency that has seen them hit military and civilian targets.

On December 3, at least nine Iraqi Kurdish peshmerga fighters and three brothers were killed in attacks claimed by IS in the northern Iraqi village of Khidir Jija, just south of the Kurdish capital Arbil.

Four more Peshmerga fighters were killed in another attack blamed on IS on December 6.

At the end of November, five peshmergas were killed in a roadside bombing claimed by the jihadist group.

IS also claimed a bombing against a market in Sadr city, a Shiite suburb of the capital Baghdad, that killed dozens of people in July last year.

IS also maintain a presence in Syria, especially in desert hideouts in the east of the country, where the Kurds maintain a semi-autonomous administration and the jihadists continue to carry out attacks.

A UN report last year estimated that around 10,000 IS fighters remained active across Iraq and Syria.