The main al-Qaida breakaway group in Iraq has claimed responsibility for an audacious attack on a military barracks that left 15 troops killed.

The troops were assigned to protect an oil pipeline that sends Iraqi crude oil to international markets and guard a nearby highway outside the northern city of Mosul when the attack occurred last Monday. Eight of the soldiers were beheaded while the rest were killed by gunfire.

Along with the statement posted Sunday on a website commonly used by jihadists, the Islamic State of Iraq and the Levant put up an image of the beheading of one of the soldiers, as well as captured arms and vehicles.

The authenticity of the statement couldn't be independently verified, but its style was consistent with previous statements.