Baghdad, Nov 11 (IANS): Iraqi security forces have taken control of most parts of the country's largest oil refinery town of Baiji in Salahudin province, after fierce clashes with the Islamic State (IS) militant group, a security source said Tuesday.

Security forces backed by allied militias and aircraft took control of the main street that bisects Baiji, some 200 km north of Iraq's capital Baghdad, while the troops encroached into most of the town's districts, a provincial security source told Xinhua on condition of anonymity.

"We have seized all the government buildings in Baiji after we captured the main street, and the troops are deploying in all directions to seize all the districts after they defused dozens of roadside bombs and booby-trapped houses planted by the IS militants," the source said.

The next move after Baiji is to seize the strategic al-Fatha area, just two km north of Baiji, which is a crossroad area used by the IS to supply its militants with weapons, ammunition and food, and then to free the nearby besieged oil refinery, the source added.

On Friday, security forces launched a major offensive and gained a foothold into Baiji after fierce clashes with the IS militants. Since then, clashes and slow advance of the troops continued, while teams of explosive experts were working to defuse the roadside bombs.

The capture of Baiji would let Iraqi security forces to launch another major offensive to expel the IS militants from Tikrit, hometown of former Iraqi leader Saddam Hussein and the capital of Salahudin province, which has been under the control of the extremist Sunni militants since June 11.

The seizure of Salahudin province was part of the drastic security deterioration in the country since June 10, when bloody clashes broke out between Iraqi security forces and IS militants, who took control of the country's northern city of Mosul and later seized swathes of territories in Nineveh and other predominantly Sunni provinces.