Iraq's army chief Friday claimed a major victory in Dhuluiyah, a town north of Baghdad where a Sunni tribe has been resisting the Islamic State jihadist group for almost four months.

The Dhuluiyah fighters contacted by Agence France-Presse, however, said the town had not yet been fully liberated.

"Dhuluiyah has been completely cleared of IS," Lieutenant General Mohammed al-Askari told AFP.

"The Iraqi army, as well as volunteers from the tribes and popular brigades (Shiite militias), entered Dhuluiyah and have now reached the office of the mayor," he said.

Dhuluiyah lies about 90 kilometers (55 miles) from Baghdad and the Jubur tribe in the south of the town has held out against relentless attacks by the jihadists.

A victory against IS there has been described as crucial to efforts by the government to show it was willing to support Sunni tribes rejecting IS.

"The army arrived from the north and moved into areas close to the Khazraj district" which has been under IS control for the best part of the past four months, said one fighter in Dhuluiyah, Abu Haitham al-Juburi.

He said the operation was coordinated with another tribe, the Albu Faraj, and explained that pro-government forces had left an escape route open for the jihadists in order to avoid more bloodshed.

"The officer in charge decided not to attack Khazraj tonight in order to minimize casualties. We will go there tomorrow," he said.