BAGHDAD - Iraqi security forces launched Saturday a major offensive to retake control of the city of Tikrit, the capital of the Sunni-dominant province of Salahudin, which has been seized by the Sunni militants earlier in the month, a security source said.

Dozens of military vehicles, backed by tanks, armored vehicles and helicopter gunships advanced in the early morning from four routes towards the city of Tikrit, some 170 km north of the Iraqi capital of Baghdad, the source told Xinhua on condition of anonymity.

The main route of the troops was launched from the areas near the city of Samarra, some 50 km south of Tikrit, but the security forces were stopped by the Sunni militants in an area near the town of Dijla, some 25 km south of Tikrit, the source said, adding that the gunmen booby-trapped the buildings and all the roads leading to Tikrit to hamper the troops advance.

Iraqi aircraft carried out intensive air strikes in and around the city of Tikrit, targeting the posts of the Sunni militant, including those who are linked to the Islamic State in Iraq and Levant (ISIL), an al-Qaida offshoot, the source said without giving further details.

On June 11, militant groups took control of the city of Tikrit when hundreds of gunmen entered the city during the advance of the Sunni militants.

The seizure of Tikrit was part of deterioration in security which started in province of Nineveh earlier in the month when bloody clashes broke out between security forces and Sunni militants, who have seized several key Iraqi cities, and large swathes of territories in several Sunni provinces, including the province of Salahudin and its capital Tikrit, the hometown of former president Saddam Hussein.