The director of Russia's FSB has said the United States, Britain and Ukraine were behind the Moscow concert hall attack that killed at least 139 people.
Alexander Bortnikov said they believe "the action was prepared by both the radical Islamists themselves and facilitated by Western special services," he was quoted by Russian news agencies as saying.
He added that Ukraine’s special services themselves have a direct connection to the attack and repeated the Kremlin's claim that the attackers tried fleeing over the Ukrainian border.
However, the President of Belarus said the attackers tried fleeing to his country first but turned around because of checkpoints, contradicting Russia's claim they tried crossing into Ukraine first.
Alexander Lukashenko said "there was no way they could enter Belarus, they saw that and that's why they turned away and went to the section of the Ukrainian-Russian border".
A Russian court has remanded an eighth suspect in custody over the attack, officials said.
Earlier, Russia announced it had detained 11 people in connection with the attack, which saw camouflaged gunmen open fire at people at a concert in Crocus City Hall and set the building on fire.
Russian State media said the latest suspect is a man from Kyrgyzstan.
Officials said he was ordered to be held in detention until at least 22 May, without detailing the exact accusations against him.
Four men charged on Sunday with carrying out the attack are citizens of Tajikistan.
Three more suspects - reportedly from the same family and including at least one Russian citizen - were charged on terror-related offences yesterday.
It is the worst such attack on Moscow in over two decades and was claimed by the Islamic State group on Friday.
Ukraine has described accusations it was involved as absurd.
