ISLAMIC State in Iraq and the Levant (Isis) forces proclaimed a new caliphate today in the territories they hold in Iraq and Syria.

They declared the group’s leader Abu Bakr al-Baghdadi the new caliph and demanded that Muslims everywhere swear loyalty to him.

“The legality of all emirates, groups, states and organisations becomes null by the expansion of the caliph’s authority and the arrival of its troops to their areas,” said Isis spokesman Abu Mohammed al-Adnani. 

“Listen to your caliph and obey him. Support your state, which grows every day.”

The spokesman defined the caliphate’s territory as running from northern Syria to the Iraqi province of Diyala, north-east of Baghdad.

He added that with the establishment of the caliphate the group was changing its name to simply the Islamic State, dropping mention of Iraq and the Levant.

The announcement coincided with the continuation of the Baghdad government’s offensive centred on the city of Tikrit.

Isis has built an alliance of convenience with Sunni forces alienated by the discriminatory policies of Iraqi Prime Minister Nouri al-Maliki’s government.

Demobilised members of the armed forces loyal to executed dictator Saddam Hussein have also thrown their lot in with the jihadists, although the Isis statement demanding sole authority and submission may affect the stability of such alliances.

Rival Islamist rebel group the Army of Islam attacked “the gangs of al-Baghdadi” for living in a fantasy world.

“They’re delusional. They want to establish a state, but they don’t have the elements for it,” said Army of Islam spokesman Abdel-Rahman al-Shami.

“You cannot establish a state through looting, sabotage and bombing.”

Sunni member of the Iraqi parliament Hamid al-Mutlaq said: “This is a project that was well-planned to rupture society and to spread chaos and damage. This is not to the benefit of the Iraqi people and it will increase differences and splits instead.”

Iraqi government spokesman Ali al-Moussawi stressed the terrorist nature of Isis, which should be fought, but said: “Regrettably, there are some people, the tribal revolutionaries, providing cover for it.”