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Reuters has indicated that the detained individuals are foreigners, though it was not specified which countries they are from.
According to the FSB, one of the four men apprehended admitted to directly supplying the assailants with weapons in Krasnogorsk, near Moscow.
A video of a foreigner's interrogation, detained in Dagestan, was made public by law enforcement. The man confesses in the video to providing weapons to those accused of launching a terrorist attack on Crocus City Hall, as reported by the Russian portal Sota.
On Sunday, the Russian National Anti-Terrorist Committee (NAK) announced the arrest of three individuals during an "anti-terrorist operation" in Dagestan. The NAK stated that these men were allegedly plotting "terrorist-related crimes". They were found with automatic weapons, ammunition, and a homemade explosive device that was ready for use.
On 22 March, an attack occurred in a concert hall in Krasnogorsk, near Moscow, resulting in at least 144 people being killed and approximately 551 injured. The Islamic State of Khorasan Province, the Afghan branch of the terrorist group IS, claimed responsibility for the attack.
Despite this, Russia initially pointed fingers at Ukraine for the incident. On Saturday, the Kremlin formally accused Ukraine of orchestrating the terrorist attack at Crocus City Hall. It demanded the arrest and extradition of everyone linked to the incident, including the head of the SBU, Vasyl Malyuk. In retaliation, the Security Service of Ukraine highlighted that "Putin is officially on the international wanted list".