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An audio recording believed to be the voice of Osama Bin Laden's youngest son has emerged online, raising the spectre that al-Qaeda is attempting a comeback as the Islamic State group suffers heavy losses in Iraq and Syria.

The audio recording of Hamza Bin Laden, 28, was first aired on May 13 and appeared online across extremist Islamic websites calling for attacks against the West, The Washington Post reported.

"Prepare diligently to inflict crippling losses on those who have disbelieved," the voice says. "Follow in the footsteps of martyrdom-seekers before you."

A Middle Eastern security official who spoke to the Post said that using Hamza Bin Laden as a figurehead to re-launch the group is a highly symbolic, and could be a powerful recruitment tool.

"Al-Qaeda is trying to use the moment — [with] Daesh being under attack — to offer jihadists a new alternative," the official said, speaking on the condition of anonymity.

The Islamic State has been losing ground steadily for close to two years now, and is now thought to control less than seven percent of Iraq, down from the 40 percent it held in 2014.

The most brutal organisation in modern self-proclaimed 'jihad' shocked the world when it took over Mosul in June 2014.

It now controls just 10 percent of the western part of the city following a seven-month US-backed campaign by Iraqi forces. In Syria, US-backed Kurdish forces are preparing for an assault on Raqqa, once the Islamic State's de facto capital.

"At a time when [Ayman] Zawahiri and al-Baghdadi seem to be fading, Hamza is the heir apparent," Bruce Riedel of the Brookings Institution said of the recent recording in comments to the Post.

Osama bin Laden was renowned for carefully planned, large-scale terrorist attacks such as 9/11 and US embassy bombings in East Africa, but Hamza appears to advocate lone-wolf attacks on a variety of soft targets in his latest recording, mimicking the tactics used by the Islamic State.

"It is not necessary that it should be a military tool," the youngest bin Laden says in the recording. "If you are able to pick a firearm, well and good; if not, the options are many."

Last year, an audio recording posted online featured Hamza bin Laden promising to continue Al-Qaeda's fight against the United States and its allies, threatening revenge for his father's assassination.

Bin Laden was introduced in the recording by Al-Qaeda's new head, Ayman al-Zawahiri, leading many to believe that a new, younger figurehead directly connected to the group's founder was being touted to lead the organisation.

There are no confirmed photographs of Hamza since his childhood, and while he lived for a time in the tribal area of north-western Pakistan, his current whereabouts are unknown.