The Islamic State group (IS) has claimed responsibility for Friday's attack on a Moscow concert hall that killed more than 100 people -- terrorism experts say its Afghan branch is likely responsible.

Since the fundamentalist Taliban took over Kabul, the ISKP -- the Afghan branch of IS -- has managed to poach members from its rival movement and has repeatedly shown off its will and capability to strike outside Afghanistan's borders.

An August 2021 blast claimed by the group killed 100 civilians and 13 American soldiers at Kabul airport -- just as the United States was withdrawing from the Afghan capital and the Taliban laid their hands on power.

It was the deadliest-ever attack by IS against the US.

Washington offered a $10 million reward for information on ISKP's leader Sanaullah Ghafari, also known as Shahab al-Muhajir.

Born in 1994, he is "responsible for approving all ISIS-K operations throughout Afghanistan and arranging funding to conduct operations," according to the US State Department, which uses an alternative acronym for the ISKP.

The US foreign ministry placed Ghafari on its foreign terrorist blacklist in November 2021.

  'Close connections to centre' 

 Afghanistan's IS branch was built by the group's envoys arriving from Iraq and Syria -- unlike almost everywhere else in the world, where pre-existing outfits pledged to its cause, said Hans-Jakob Schindler, director of the Counter Extremism Project (CEP) research outfit and a former UN terrorism expert.

"They have very close connections to the centre, much more than the other affiliates," Schindler told AFP, adding that this gives them access to ample funding.

Lucas Webber, co-founder of specialist website Militant Wire, highlighted that the "ISKP has emerged as the most internationally minded IS branch... producing propaganda in more languages than any other branch since the height of the caliphate in Iraq and Syria."

It has been mounting an "ambitious and aggressive campaign to bolster its external operations capabilities and strike its various enemies abroad," he added.

  On the radar 

 Both Western and Russian security services have long been monitoring ISKP.

On Tuesday, German authorities arrested two Afghan suspected jihadists, believed to have been planning an attack on the Swedish parliament.

Public burnings of the Koran have increased the terrorist threat against Stockholm.

One of the two men is alleged to have travelled from Germany to join ISKP.

Germany had previously dismantled a Russian-Tajik network in 2020, with more groups targeted in 2022 and 2023.

Russian authorities said on March 7 they had killed suspected ISKP members in an operation in the Kaluga region southwest of Moscow.

Officials said the people had been planning an attack on a synagogue in the capital.

Kazakhstan said two of its citizens were killed in the operation.

  Sights on Russia 

 Russia has become a priority target for ISKP, which condemns its invasion of Ukraine and its military interventions across Africa and in Syria, Webber said.

A 2022 suicide bombing targeted Russia's embassy in Afghanistan.

ISKP "is working to extend its reach throughout Central Asia and Russia," Webber added, putting together "a Russian language media wing to build support and incite violence inside the country".

Schindler said that with Moscow's attention on the invasion of Ukraine, Russia is a more tempting target.

Friday's attack -- relatively cheap and straightforward to put together -- was "a big symbol", he added.

"Its hard to overestimate how important today’s attack in Moscow is for the Islamic State and what it tells about its evolution," Tore Hamming of the International Centre for the Study of Radicalization posted on X, formerly Twitter, on Friday.

"IS had worked since 2019 to reestablish an institutional unit in charge of external operations," Hamming added, "first in Turkey and later in Afghanistan with Central Asians as key actors."

"Based on a recent high number of foiled plots and today’s attack, it appears they are succeeding," Hamming said.

ISKP now has "Afghanistan and Central Asia as a hub to target Russia/Asia and Turkey as a gateway to Europe," he added.