Iraqi government forces backed by helicopter gunships began an offensive yesterday to retake the northern city of Tikrit from Sunni Islamist militants Isis while party leaders pursued talks that could end Prime Minister Nouri al-Maliki's divisive rule.

Politicians warn that unless security forces recover cities lost to the jihadi insurgents in tandem with a rapid formation of a government that can bring Iraq's estranged communities together, the country could rip apart along sectarian lines.

On the battlefield, Iraqi troops were trying to advance on Tikrit from the direction of Samarra to the south that has become the military's line in the sand against a militant advance southwards towards Baghdad.

Loading article content

Iraqi special forces have snipers inside Tikrit University who were dropped by air in an operation on Thursday. Helicopter gunships fired at targets in Tikrit yesterday and Isis fighters abandoned Tikrit's governorate building, security sources said.

The militants are showing resilience and have the backing of some Sunni tribes, as well as Baathists alienated from Maliki's government.

In other areas, such as Jurf al-Sakhar, 53 miles south of Baghdad, militants from Isis were on the offensive. Three police sources said at least 60 Isis fighters had been killed along with more than 15 Iraqi security forces members when the militant group launched an attack on an army camp east of Jurf al-Sakhar.

In a stunning political intervention on Friday that could mean the demise of Maliki's eight-year tenure, powerful Iraqi Shi'ite cleric Grand Ayatollah Ali Sistani urged political blocs to agree on the next premier, parliament speaker and president before a newly elected legislature meets in Baghdad on Tuesday. Saudi King Abdullah pledged in talks with US Secretary of State John Kerry to use his influence to encourage Sunni Muslims to join a more inclusive Iraqi government to better combat Islamist insurgents, a US official said. Abdullah's assurance marked a huge shift from Riyadh's unwillingness to support a new government unless Maliki, a Shi'ite, steps aside, and reflected growing disquiet about the repercussions of Isis's rise.

Maliki, whose State of Law coalition won the most seats in the April election, was positioning himself for a third term before the Isis offensive began. His closest allies say he still aims to stay, but others coalition believe he could be replaced with a less polarising figure.