IS militants captured over 40 people from the albu-Obeid Sunni tribe, including policemen and members of the government-backed Sahwa paramilitary group, in al-Baghdadi town, and executed them, Xinhua cited the official, who did not wish to be named, as saying.
The targeted town is located near the major air base of Ain al-Asad which houses hundreds of US troops.
The battles in and near al-Baghdadi have continued since Thursday when IS militants attacked the town and nearby Ain al-Asad air base and seized the town.
However, their attacks on the air base were repelled by security forces and US aircrafts, while fighting continued in the town after Iraqi troops regained control of large parts of it.
IS militants laid siege to a neighbourhood in the town housing dozens of families of security members and Sahwa fighters, said the official.
He added that residents were fighting back IS attacks but were facing acute shortage of food, drinking water, weapons and ammunition.
IS militants Saturday executed 33 people in the town. Many were local policemen and Sahwa members.
Ain al-Asad military base is used by Iraqi military forces, as well as roughly 300 US Marines in their capacity as military trainers and advisers.
The IS group has seized around 80 per cent of Iraq’s largest province of Anbar and has been trying to advance toward Baghdad. But several counter attacks by security forces and Shia militias pushed them back from western areas of the capital.
Since December last year, there have been insurgent attacks in the Sunni Arab heartland west of Baghdad which stretches through the Anbar province.
The security situation in Iraq started drastically deteriorating June 10, when bloody clashes broke out between Iraqi security forces and IS, an Al Qaeda offshoot.
IS took control of the country’s northern province of Nineveh, later seizing swathes of territories once Iraqi security forces abandoned their posts in other predominantly Sunni provinces.