Isis chief Abu Bakr al-Baghdadi
Abu Bakr al-Baghdadi was believed to have been seriously injured in a coalition airstrike.Reuters

Islamic State has released an audio message believed to be from its leader Abu Bakr al-Baghdadi.

The audio recording has been published on several militant websites and while analysts believe the voice appears to be al-Baghdadi's, this has not yet been verified.

If it is authentic, it marks the first time the leader of the terror group has been seen or heard from in months.

In the message released by the group's al-Furqan media outlet, he urges Muslims to take up arms on behalf of Isis and emigrate to the "caliphate" it has proclaimed in areas of Syria and Iraq.

He makes references to the Saudi-led air campaign against Shia rebels in Yemen, which began on 26 March and criticises the Saudi royal family.

The message has surfaced a month after it was first reported that al-Baghdadi was no longer in day-to-day command of IS after being seriously wounded in a coalition airstrike.

He was apparently hit by shrapnel "all over his body" as the convoy he was travelling in was struck by a coalition aerial raid in western Iraq in March, leaving him with spinal injuries.

The claim was made by Dr Hisham al Hashimi, a regional adviser to the Iraqi government, citing a source in the Mosul hospital which treated him.

IS deputy leader Abu Alaa Afri, a former physics teacher who is believed to have assumed control of the extremist Sunni organisation, was later reported to have been killed in an air strike, according to the Iraqi government.

In the wake of reports that he had been killed or injured, IS released a 17-minute audio recording of al-Baghdadi calling for followers to "erupt volcanoes of jihad everywhere". Al-Baghdadi has appeared in public only once, in a video showing him delivering a Friday sermon in Mosul last July.

In the past al-Furqan has distributed videos of mass executions and killings by IS, while Baghdadi has used audio announcements to call for Muslims to join the self-described caliphate the group has established in Iraq and Syria.