Beirut: Daesh insurgents in Iraq and Syria have issued a pamphlet calling for Muslims to pledge loyalty to their chief, Abu Bakr Al Baghdadi, pressing a campaign to establish a “caliphate” even as US-led forces bomb their positions.

Al Baghdadi’s claim to the mantle of Islam’s caliphate, the Muslim state established by the Prophet Mohammad’s (PBUH) first followers after his death, has infuriated many Islamic leaders and ignited an ideological battle for legitimacy. Daesh calls itself the “Islamic State”.

Islamist sources in Syria said the pamphlet, distributed widely online by supporters of the Al Qaida offshoot, was a step in the group’s campaign to establish the caliphate and familiarise people with Al Baghdadi.

Entitled “Extend your hands and pledge loyalty to Al Baghdadi”, the pamphlet appeared to be based largely on a longer statement written last year by Daesh religious figure Turki Al Bin Ali arguing why Al Baghdadi deserved to command the loyalty of believers.

Addressing itself “to whoever fought and still fights in the path of God ... to commanders of groups,” the pamphlet traced Al Baghdadi’s purported lineage to the Prophet Mohammad, outlined his studies of Islamic law, and listed his battlefield achievements while asking supporters to unite against the group’s enemies.

A coalition of the United States and Arab allies has been carrying out air strikes against Daesh in Syria.

“Isn’t it time for you to unite with your brothers? To establish and elevate your state? The enemy has allied to fight you, so unite to fight him,” said the pamphlet.

The US-led campaign has pushed some members of Al Qaida’s affiliate in Syria, the Nusra Front, to pressure their leaders to reconcile with Daesh after the two groups clashed earlier in the year.

Among other historical religious scholars, the pamphlet quoted Mohammad Ibn Abd Al Wahhab, founder of Saudi Arabia’s Wahhabi school of Islam, whose 18th century alliance with the Saudi ruling family continues to underpin the country’s politics.

The kingdom’s religious establishment has campaigned against militancy in recent weeks, describing both Daesh and Al Qaida as Islam’s foremost enemy. In August, the country’s Grand Mufti urged young people to ignore calls to jihad from people representing “deviant principles”.

One Islamist fighter in Syria who is not an Daesh member said the group regarded issuing biographical detail about Al Baghdadi as a necessary step in establishing him as caliph.

“After this statement it is now official in their eyes that it is the duty of Muslims to pledge allegiance to him,” the fighter said. “They are telling the world, ‘Here is our Commander of the Faithful.’” Daesh has its roots as Al Qaida’s affiliate in Iraq, but split with the central organisation headed by Ayman Zawahri this year after falling out over its expansion into Syria.

Leading figures affiliated with Al Qaida this week launched an initiative to establish a “truce” with Daesh and asked the group to respond by the Muslim holiday of Eid Al Adha, which starts on Saturday.

The rise of Daesh has appeared to capture the imaginations of at least some militants previously affiliated with Al Qaida.

Algerian Islamist militants who pledged their loyalty to Daesh kidnapped and beheaded a French hostage last month and militants in the southern Philippines have threatened to kill two German hostages in a show of solidarity with Daesh.

“Extend your hands to pledge allegiance to Baghdadi,” the Daesh pamphlet said. “It is a wonder that some people - who are not among you - are content to give allegiance to tyrants for years, but not to give allegiance to the commander of the faithful.”