Baghdad: At least 81 people were killed Wednesday in airstrikes and clashes between the Iraqi forces and militants, security sources said.

In Salahudin province, north of Baghdad, Iraqi security forces backed by allied forces launched an offensive in the early morning hours against militants of the Islamic State (IS).

The Al Qaeda offshoot has been seizing a cluster of villages scattered west of the town of Tuz-Khurmato, some 90 km east of the provincial capital city of Tikrit, a provincial security source, speaking on condition of anonymity, told Xinhua.

The pro-government troops initially faced stiff resistance from the IS militants, but heavy fire and airstrikes enabled them to retake control of five villages and forced the IS militants to withdraw towards the west.

The militants planted dozens of bombs on roads and the buildings to slow the advance of the troops, the source said.

The offensive also targeted IS positions in other areas, north of the town of Amerli, some 70 km east of the militant-seized city of Tikrit, aiming to seize the main road between Tuz-Khurmato and Tikrit.

"The main target for the security forces is to catch the main road and a bridge leading to Tikrit. Later, the troops will have only 50 km of uninhabited plain to push to the west to free the provincial capital of Tikrit," the source said.

Salahudin province is a predominantly Sunni province and its capital Tikrit, some 170 km north of here, is the hometown of former president Saddam Hussein.

The city has been under control of the Sunni militants since June 11, a day after bloody clashes broke out between Iraqi security forces and the militants who had taken the country's northern city of Mosul and later seized swathes of territories in Nineveh and other predominantly Sunni provinces.