Islamic State has released an audio message purportedly from its leader - the first time he has been seen or heard from in months.

Several militant websites have posted the message, claiming it features the voice of Abu Bakr al Baghdadi - though this has not been verified.

The speaker references the Saudi-led air campaign against Shia rebels in Yemen, which began on 26 March.

He also criticises the Saudi royal family.

It comes a month after reports that al Baghdadi was no longer in day-to-day command of IS after being seriously wounded in an 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.

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.

The audio message, his first since November, was released by the group's al-Furqan media outlet.

Al Baghdadi has appeared in public only once, in a video showing him delivering a Friday sermon in Mosul last July.

His resurfacing follows a claim by Iraq's defence ministry on Wednesday that his second in command, Abu Alaa al-Afari, was killed in a coalition airstrike in Tal Afar, northern Iraq.

Meanwhile, IS militants are fighting government forces near the ancient city of Tadmur - one of Syria's world heritage sites.

The jihadist group has already destroyed antiquities in Iraq.

Syria's antiquities chief Maamoun Abdulkarim said the fighting was just a mile from Tadmur and that if IS takes control "they will destroy everything that exists there".

An IS fighter has told journalists they are attacking areas around the town's prison where some of its members are believed to be held.

"The airport is also a major weapons depot," the fighter said. "We want these weapons."

IS has taken control of large swathes or Iraq and Syria and declared it a "caliphate", prompting US-led airstrikes.