MOSCOW, May 24 (Reuters) - Ukrainian military intelligence was directly involved in a deadly attack on a concert hall near Moscow in which over 140 people were killed, the head of Russia's Federal Security Service (FSB) Alexander Bortnikov said, TASS reported on Friday.

Russia has made such allegations before. Bortnikov did not provide evidence to underpin his assertion.

"The investigation is ongoing, but it is already safe to say that Ukrainian military intelligence is directly involved in this attack," the state news agency quoted Bortnikov as saying.

He also accused the NATO military alliance of faciliting the transfer of "mercenaries and militants of international terrorist organisations from the Middle East, North Africa and Afghanistan" to Ukraine so that they could fight against Russian forces there.

Islamic State claimed responsibility for the concert hall massacre in March and U.S. officials said they had intelligence showing it was carried out by the network's Afghan branch, Islamic State Khorasan. Ukraine has repeatedly denied it had anything to do with the attack.

Bortnikov was cited by TASS as saying that Islamic State Khorasan had played a role in coordinating the attackers' actions and that Ukrainian military intelligence had also played a direct role.

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