But the group, which had ruled over swathes of Syria and Iraq before being defeated there, still has active branches in other parts of the world, including West Africa and Afghanistan.

Many questions remain unanswered around the death of Abu Hasan al-Hashimi al-Qurashi, announced Wednesday by an IS spokesman and later confirmed by the US military's Central Command, which said he had been killed by Syrian rebels in mid-October.

Hashimi's seven months of clandestine rule were characterised by silence, leaving countless other questions on the direction in which IS may be headed.

"You could argue that he had the least impact of any ISIS leader since the group's inception," said Colin Clarke, director of research at US-based intelligence and security think-tank Soufan Group, using an alternative acronym for IS.

More than a month had elapsed between Hashimi's death and the group's statement, during which "ISIS was likely scrambling internally to line up a replacement", the expert told AFP.

This may indicate "the group is under extreme pressure from multiple adversaries and has less freedom of manoeuvre than in the past, including in a more restricted ability to communicate with supporters and followers," Clarke said.

None of the experts contacted by AFP could provide any information concerning the new leader, Abu al-Hussein al-Husseini al-Qurashi, whose nom de guerre carries on a reference to Prophet Mohammed's tribe.

The new self-proclaimed caliph seeks to draw legitimacy by claiming heritage from the prophet's Quraysh tribe -- as did all IS leaders before him.

"The Qurashi name is used as a branding for the leader," Hans-Jakob Schindler, director of the Counter-Extremism Project think-tank, told AFP.

"Even if it is just a made up name... it is sufficient for the network to function."

- No more allies -

After a meteoric rise in Iraq and Syria in 2014, IS saw its so-called caliphate collapse, reduced to a network of sleeper cells.

In 2019 it was defeated in Syria -- where Hashimi was said to have been killed in October by local fighters.

"Syria is simply not a safe haven for ISIS anymore," said Schindler. "They can maintain a cell structure, but it is apparently not safe for high-ranking personnel there.

"If you are killing everyone, in the end no one is your ally anymore," the expert said.

Left without a sanctuary or charismatic leader, IS has lost the capacity it had under founder Abu Bakr al-Baghdadi to recruit foreigners.

And Baghdadi's successors last for increasingly shorter periods, with the last two leaders perishing without having issued any audio or video statements.

"There is likely pressure building on ISIS... to gain some momentum, particularly if the group wants to remain relevant," said Clarke of Soufan Group.

- Greater autonomy -

Still, the jihadist network affiliated with IS remains not only alive, but also deadly.

The IS-Khorasan outfit has some leverage over the Taliban regime in Afghanistan and the group has maintained some capacity to cause harm in both Iraq and Syria.

But IS has seen its most striking rise recently across Africa, with a presence in the Sahel region, through to Lake Chad, all the way down to Mozambique and in Somalia.

Global jihadism experts have noted in recent years that IS, like Al-Qaeda, has moved to decentralise its operations and rely on local groups to take over territory during crises.

The death of yet another leader and his replacement are a testament to that.

"The vulnerability of the organisation's high command boosts the autonomy of its affiliates, particularly the most active ones in Afghanistan and the Sahel," explained Jean-Pierre Filiu, a radical Islam analyst teaching at the Sciences Po university in Paris.

But recent events raise questions over how long figures in the Middle East can claim leadership.

"It is a bit discriminatory that always an Arab guy from the Quraysh tribe will have to lead this network," Schindler said.

"Let's see how many more times the African parts of the network are going to accept this."

Throughout 2021, the group's official weekly publication al-Naba dedicated 28 out of 52 front pages to African affiliates, according to a tally by Damien Ferre, founder of the Jihad Analytics group.

Indeed, seven out of IS's current 13 "provinces" are located in Africa.

But for the time being, the Arab primacy remains uncontested.

"It would require Africans to go to the Iraq-Syria area and gradually impose themselves by rising in the hierarchy," argued researcher Djallil Lounnas of Morocco's Al Akhawayn University.

But "the weaker the central power gets, the more the African affiliates can increase their power".