Iraqi forces achieved the first goal of a new offensive against the Islamic State group on just its second day Friday, penetrating the northern town of Sharqat, AFP correspondents said.

Some residents celebrated in the streets as government troops and paramilitaries entered the town centre and tore down the black flags of the jihadists who had ruled it with an iron fist for more than three years.

AFP correspondents saw little major damage in the town, although there had been casualties in the fighting as they saw the bodies of two jihadists in the back of a pickup.

Sharqat was the first goal of a major offensive launched on Thursday to recapture an IS-held enclave centred on the insurgent bastion of Hawija, one of just two pockets still controlled by the jihadists in Iraq.

Sector operations chief General Abdel Amir Yarallah said some 20 villages around Sharqat had also been recaptured from IS.

The next goal is Hawija itself, some 30 kilometres (20 miles) to the southeast.

After the defeat of IS in second city Mosul in July and the recapture of adjacent areas, Hawija and neighbouring towns form the last enclave still held by IS in Iraq apart from a section of the Euphrates Valley downstream from the border with Syria.

The mainly Sunni Arab enclave, which was bypassed by government forces in their advance north to Mosul last year, has been a bastion of insurgency ever since the first year of the US-led occupation in 2003.

The territory still held by IS in the "caliphate" straddling Iraq and Syria it proclaimed in 2014 has dwindled, with stronghold after stronghold coming under assault on both sides of the border.

Iraq soldiers, police and paramilitaries launched an offensive against the jihadists's other remaining enclave earlier this week, pushing up the Euphrates Valley towards the IS-held towns of Anna, Rawa and Al-Qaim.