Russian Federal Security Service (FSB) Director Aleksandr Bortnikov
© Sputnik/Gavriil GrigorovRussian Federal Security Service (FSB) Director Aleksandr Bortnikov attends a meeting of the Federal Security Service (FSB) Board in Moscow, Russia.
More than 20 people have been detained in connection with the assault at the Crocus City Hall, service chief Aleksandr Bortnikov has said.

Ukrainian military intelligence was directly involved in the deadly terrorist attack at the Crocus City Hall just outside Moscow in March, the director of Russia's Federal Security Service (FSB), Aleksandr Bortnikov, has said.

He added that the investigation into the attack is still being conducted, but all indications are that Ukraine was behind the assault.
"The investigation is ongoing, but we can already say with certainty that Ukraine's military intelligence has a direct relation to this attack," Bortnikov said at a Commonwealth of Independent States (CIS) special services leaders' gathering in Bishkek, Kyrgyzstan.
He said the preparation and financing of the attack, as well as the terrorists' escape from the scene afterwards, was coordinated over the internet by members of Wilayat Khorasan, also known as Islamic State - Khorasan, or ISIS-K.

He added that two of the four criminals involved arrived in Russia from Türkiye shortly before the attack. Upon completion, he said, "the terrorists received a clear command to move to the Ukrainian border, where a 'window' had been prepared for them."

The results of the investigation apparently confirm the FSB's initial version of Ukraine being behind the attack. In April, the FSB director suggested that Ukrainian security services may have been involved in preparing the assault, possibly using the Islamists as proxies. He stressed that "all the circumstances of the crime will be established," and those involved in this "heinous" terrorist attack "will not escape punishment."
"We are currently establishing the full circle of those involved in the massacre. More than 20 people have already been detained, including the direct perpetrators and accomplices," he said. Bortnikov added that "colleagues from Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan" are assisting the FSB investigation.
The attack on the concert venue just outside Moscow on March 22 claimed more than 140 lives and left over 550 injured. Four gunmen stormed the building, shooting everyone in sight before setting it on fire.

Kiev has denied any involvement in the attack, while its Western backers have claimed that all evidence points to ISIS-K as the culprit. The group has claimed responsibility for the attack.