Russia has filed charges against four men accused of attacking a concert hall in Moscow, resulting in at least 137 deaths.
All four suspects appeared to show signs of physical abuse, and one arrived in court in a wheelchair. They face charges for acts of terrorism.
The Islamic State group, also known as IS, claimed responsibility for Friday's incident at Crocus City Hall, sharing video evidence online.
Russian authorities have alleged, without supporting evidence, involvement from Ukraine, a claim dismissed as "ridiculous" by Kyiv.
On Monday, three days after the incident, President Vladimir Putin informed senior officials that the attack was orchestrated by radical Islamists, adhering to an ideology long opposed within the Islamic world.
Putin also alleged a connection between the attackers and the Ukrainian government, asserting Kyiv facilitated their entry into Russian territory.
Ukraine's President Volodymyr Zelensky refuted this accusation, calling it predictable for Putin to shift blame to Ukraine rather than address internal Russian issues.
On Monday, Putin further claimed that Kyiv, which he termed a "neo-Nazi regime," orchestrated the attack to "spread panic in our society and reassure their own people that hope remains for the Kiev [Kyiv] regime."
Graphic footage released by IS, depicting attackers shooting at the crowd inside the concert hall, has been verified as authentic by the BBC.
On Friday night, four gunmen stormed the Crocus City Hall in Krasnogorsk, a northern Moscow suburb, and began shooting at some of the roughly 6,000 concert attendees. The attackers also set fires that engulfed the venue and caused the roof to collapse.
Russian authorities reported that 137 people lost their lives, with over 100 injured, including 60 in serious condition.
Rescue teams continue to search through the concert hall debris, with local officials stating the efforts would persist through Tuesday afternoon.
The men seen in court on Sunday were detained in the Bryansk region about 14 hours post-attack, according to Russia's Federal Security Service (FSB). Bryansk is approximately 400km (250 miles) southwest of Moscow. The US had warned Moscow earlier this month of a potential attack on large gatherings before issuing a public advisory for its citizens in Russia.
The alert was largely dismissed by the Kremlin, labeling it propaganda intended to interfere with its presidential election.
Following the incident, Washington stated it had no grounds to doubt IS’s responsibility claim.
This incident marks another instance of IS and its affiliates targeting Russia or Russian interests abroad.
The group previously claimed responsibility for the 2015 bombing of a Russian aircraft over Egypt, which killed 224 people, mostly Russian nationals, and a 2017 bombing on the St. Petersburg metro, which resulted in 15 fatalities.
Security experts believe IS considers Russia a prime target for several reasons, including Moscow's role in defeating IS's stronghold in Syria while reinforcing President Bashar al-Assad’s government, Russia's two brutal conflicts in Muslim-majority Chechnya from 1994-2009, and the Soviet Union’s invasion of Afghanistan.
US and Western intelligence suggest the attack was likely conducted by the Khorasan branch of IS, known as Isis-K, active mainly in Afghanistan and parts of Central Asia.
Isis-K, one of the most capable and active IS branches, was responsible for deadly suicide bombings at Kabul airport during the US withdrawal in August and September 2021.
Isis-K frequently targets President Vladimir Putin in its propaganda efforts.
