MOSCOW

Head of the Russian Federal Security Service Aleksandr Bortnikov on Friday accused Ukraine of direct involvement in the April 22 terrorist attack on Crocus City concert hall in the Moscow region.

"The investigation is underway, but it is already safe to say that the military intelligence of Ukraine is directly involved in this attack," Bortnikov said at a meeting of the heads of the Commonwealth of Independent States security agencies and special services.

Bortnikov stressed that all circumstances of the crime will be established and all guilty parties -- punished.

On March 22, gunmen entered the Crocus City Hall in Krasnogorsk, Moscow Oblast, and sprayed bullets at random on innocent people, killing at least 144 and injuring more than 382. Russia has charged four people for their direct involvement in the attack.

According to investigators, after committing the crime, the suspects were heading toward Ukraine, where they hoped to find shelter and evade justice.