BAGHDAD, Nov. 3  -- The Islamic State (IS) militant group executed 36 tribesmen, including women and children, in Iraq 's western province of Anbar on Monday, as part of mass killings in the past few days against a Sunni tribe which resisted the IS' advance, a provincial security source said.

The bodies of 30 men, four women and two children of Albu Nimer tribe were found executed by the so-called Islamic State firing squad, the source told Xinhua on condition of anonymity. The bodies were found dumped near the town of Heet, about 70 km west of Ramadi, Anbar province in western Iraq.

The radical group has executed more than 400 Albu Nimer tribesmen during the past few days, after the town of Heet was occupied about two weeks ago.

The IS has seized around 80 percent of Iraq's largest province of Anbar and is trying to advance toward Baghdad, but several counter attacks by the security forces and Shiite militia have pushed them away from areas west of the capital, which contains a large Shiite population and is heavily fortified by security forces and Shiite militia.

Since December last year, insurgent attacks have continued in the Sunni Arab heartland west of Baghdad that stretches through Anbar province, which has been the scene of fierce clashes that flared up after Iraqi police dismantled an anti-government protest site outside the city of Ramadi.