The Islamic State group, also known as ISIS, claimed responsibility for Friday鈥檚 deadly assault on a concert venue in Moscow, releasing graphic footage purporting to show its gunmen carrying out what was Russia鈥檚 worst terror attack in decades.
Russian authorities have accused four men from the former Soviet republic of Tajikistan of being behind the attack, which left at least 137 people dead and more than 100 injured. The suspects, who are charged with committing a terrorist act and face possible life imprisonment, have been remanded into pre-trial detention through May 22 after appearing in court in Moscow on Sunday.
U.S. officials have tied the attack to the Islamic State in Khorasan, or ISIS-K, an ISIS affiliate that operates in central Asia, which has become one of the region鈥檚 most brutal and feared terror groups.
Since November, the U.S. has received a stream of intelligence that ISIS-K was determined to mount an attack in Russia, sources told CNN, and passed those warnings on to Moscow. U.S. Vice President Kamala Harris said Sunday that 鈥渨hat we know to be the case is that ISIS-K is actually, by all accounts responsible for what happened.鈥�
Here鈥檚 what we know about ISIS-K.
What is ISIS-K?
ISIS-K was formed in 2015 and has been active in Afghanistan, Pakistan and Iran. It is a branch of ISIS, the terror group that emerged in Syria and Iraq and, at its peak, controlled a huge stretch of territory.
Five years since the fall of ISIS鈥� self-proclaimed caliphate across Iraq and Syria, the group has morphed into a terror network with cells spread around the world, including in Africa, the Middle East, Central Asia and Southeast Asia.
The connection between ISIS-K and its apparent parent group is not entirely clear. The affiliates share an ideology and tactics, but the depth of their relationship 鈥� such as the chain of command and control 鈥� has never been fully established.
By 2018, ISIS-K was ranked the world鈥檚 fourth-deadliest , according to the Institute for Economics and Peace, which monitors global terrorism.
The Taliban鈥檚 takeover of Afghanistan in August 2021, and the withdrawal of U.S. troops from the country, thrust ISIS-K into the global spotlight 鈥� especially after the group orchestrated a deadly bombing outside Kabul airport that killed 13 U.S. military personnel and 170 Afghans.
It was ISIS-K鈥檚 most globally consequential action to date and drew a promise of retribution from U.S. President Joe Biden.
The United Nations estimated in 2021 that the group has up to 2,200 core fighters based in Afghanistan鈥檚 Kunar and Nangarhar provinces.
What does it want?
Like its parent organization, ISIS-K aims to create a 鈥減ure Islamic state,鈥� according to CSIS 鈥� describing the group鈥檚 vision of a 鈥済lobal, transnational caliphate鈥� governed by Sharia law.
ISIS-K has a mutual hatred of the Taliban and attracts those with views even more radical than the Islamist group that rules Afghanistan. It refuses to acknowledge the Taliban as a legitimate Islamic leader because it relies on a narrow base 鈥渋nstead of committing to a universal Islamic jihad,鈥� according to CSIS.
As such, ISIS-K鈥檚 recent attacks have largely been aimed at the Taliban and other symbolic targets, as well as at Afghanistan鈥檚 Shia Muslim minorities, in particular the ethnic Hazaras.
The group鈥檚 hatred of the West, including the United States, Britain and Europe, also features prominently in its agenda 鈥� as does its enmity toward Russia.
Why did it attack Russia?
ISIS has a longstanding animosity against Russia and Putin, several experts told CNN.
鈥淩ussia has been at the top or near the top of the list of ISIS for many years,鈥� said Daniel Byman, director of Georgetown University鈥檚 security studies program. He pointed to Moscow鈥檚 crucial role in the Syrian civil war, when it intervened in support of the Syrian government and against ISIS.
ISIS-K has also criticized the Taliban for being 鈥渢oo close to Russia,鈥� Byman added.
There are other historical grievances, too. ISIS propaganda has long targeted Russia for its brutal tactics in the various Chechen wars, and its scorched-earth policies in the Caucasus affecting Eastern European and Eurasian Muslims, according to John Miller, CNN鈥檚 chief law enforcement and intelligence analyst.
In 2022, ISIS-K claimed responsibility for a suicide blast near Russia鈥檚 embassy in Kabul, which killed six people, including two consular staff.
Over the past month, Russia has thwarted several ISIS-related incidents, according to state-run news agency RIA Novosti. At least four incidents in March alone have been reported across Russia that local authorities said involved people connected to ISIS, RIA reported.
Russian state media reported on March 7 that the FSB, Russia鈥檚 security service, prevented an ISIS attack on a synagogue in Moscow, according to Reuters. The ISIS attackers were killed in a gunfight, the reports said.
What other attacks is it responsible for?
To date, the majority of ISIS-K鈥檚 most devastating attacks have been in Afghanistan and Pakistan 鈥� the Kabul airport blast being a prominent example.
Others include a May 2020 attack on a Kabul maternity ward that killed 24 people and an attack on Kabul University in November 2020 that killed 22, according to CSIS. ISIS-K was also believed to be behind a horrific car bombing outside a girls鈥� high school in May 2021 that killed at least 85 people.
The group was particularly active during its peak around 2018 鈥� when an ISIS-K suicide bomber killed 128 people at an election rally in Mastung, Pakistan, one of the bloodiest attacks anywhere in the world that year.
While it鈥檚 no longer as strong as it was in 2018, ISIS-K continues to plan attacks in Afghanistan. It is the most active terror group in the country, responsible for 73 deaths in 2023, according to the Institute for Economics and Peace.
Could it pose a broader global threat?
The Kabul airport attack had raised global concerns that ISIS-K could pose a major threat across the region and beyond.
In March 2023, the head of the U.S. Central Command told lawmakers that ISIS-K was becoming more emboldened, and that Europe or Asia were more likely targets for terrorist attacks originating in Afghanistan than the U.S.
In a 2023 threat assessment report by U.S. intelligence agencies, the Office of the Director of National Intelligence said ISIS-K 鈥渁lmost certainly retains the intent to conduct operations in the West and will continue efforts to attack outside Afghanistan.鈥�
And earlier this year, the UN Security Council warned in a report that ISIS-K was planning or conducting 鈥渙perational plots鈥� in Europe. Seven people linked to the group were arrested in Germany last year while planning for 鈥�,鈥� including obtaining weapons and possible targets, the council said.
It is not the first time that ISIS has struck a concert venue. In November 2015, ISIS gunmen attacked the Bataclan theatre in Paris 鈥� part of an assault that hit other targets in the city 鈥� killing at least 130 people. In May 2017, the group claimed responsibility for a suicide bombing at an Ariana Grande concert in Manchester Arena, England, that killed 22 people. ISIS has also inspired terrorists in the U.S., including the gunman who killed 49 people at the Pulse nightclub in Orlando, Fla., in 2016 in what was then the most lethal terrorist attack in the U.S. since 9/11.
Earlier this month, the U.S. government had information about a planned terrorist attack in Moscow 鈥� potentially targeting large gatherings, including concerts 鈥� which prompted the State Department to issue a public advisory to Americans in Russia. The U.S. also shared this information with Russian authorities.
The intelligence that Washington had been getting since November was 鈥渇airly specific鈥� and the U.S. intelligence community warned Russia, but it鈥檚 not clear if this is directly tied to the March 7 warning by the U.S. embassy in Moscow.
Russian President Vladimir Putin rejected the U.S. embassy warnings about terror attacks as 鈥減rovocative鈥� in a speech to the FSB, saying they 鈥渞esemble outright blackmail and the intention to intimidate and destabilize our society.鈥�
Instead, Putin suggested Ukraine was behind the Crocus City attack 鈥� which Kyiv has vehemently denied.
