Suicide attackers from the so-called ’Islamic State of Iraq and the Levant’ (ISIL) takfiri group killed at least 12 Iraqi forces Sunday in a brazen attack on police training at a military base Sunday.

Suicide attackers from the so-called 'Islamic State of Iraq and the Levant' (ISIL) takfiri group killed at least 12 Iraqi forces Sunday in a brazen attack on police training at a military base Sunday, officials said.

A commando of gunmen equipped with rifles and suicide vests snuck into Speicher base, near the city of Tikrit, in the middle of the night. Their target was a large group of police forces from Nineveh, a northern province of which Mosul is the capital, who were undergoing training.

"Under the cover of fog, they broke into Speicher," said Mahmud al-Sorchi, spokesman for the paramilitary force being set up to take back ISIL-held Nineveh province.

"Nineveh police managed to kill seven attackers but three were able to detonate their suicide vests," he said, adding that three officers were among the 12 policemen killed.

He also said 20 policemen were wounded in the attack.

ISIL claimed responsibility for the attack and said seven suicide attackers managed to enter the huge military base, which lies about 160 kilometers (100 miles) north of Baghdad.

Speicher is located in Salaheddin province, which was one of the regions occupied by ISIL when it swept across much of Iraq's heartland in June 2014.

The sprawling military base itself was never fully controlled by the terrorists but at the beginning of their offensive they committed one of the conflict's worst atrocities there.