By Guy Faulconbridge
MOSCOW (Reuters) -The director of Russia's most powerful security agency said on Tuesday that he believed Ukraine, along with the United States and Britain, were involved in the attack on a concert hall just outside Moscow that killed at least 139 people.
Ukraine, which has repeatedly denied any link with Friday's attack, dismissed the Russian accusations as lies. Britain said they were "utter nonsense". Islamic State, the militant group that once sought control over swathes of Iraq and Syria, claimed responsibility for the mass shooting.
"We believe that the action was prepared by both the Islamist radicals themselves and was facilitated by Western special services," Alexander Bortnikov, director of the Federal Security Service (FSB), said on television.
"The special services of Ukraine are directly related to this," Bortnikov said, adding Kyiv had helped prepare Islamist radicals at an unidentified location in the Middle East.
When asked by Russian reporters if Ukraine and its allies, the United States and Britain, were involved in the attack on the concert hall, Bortnikov said: "We think that's the case. In any case, we are now talking about the texture that we have. This is general information."
Bortnikov, 72, who has served as head of the FSB since 2008, said Russia had yet to identify those who specifically ordered the deadliest attack inside Russia for two decades, but said that retaliatory measures would be taken.
He offered no specific evidence for the claims, which hardliners in Moscow could use to justify an escalation of the war in Ukraine and to explain how Russian security services failed to prevent the attack.
Since President Vladimir Putin sent forces into Ukraine in 2022, the Kremlin has cast the West - and particularly the United States and Britain - as enemies whose decision to support Ukraine essentially outs them as parties to war with Russia.
Russia has repeatedly said that blasts on the Nord Stream gas pipelines under the Baltic Sea in September 2022 were carried out by the United States and Britain. Washington and London have denied those accusations.
'ISIS OR UKRAINE?'
Russian news outlet SHOT published a video of an exchange in which a reporter asked Nikolai Patrushev, the secretary of Russia's Security Council, whether it was "ISIS (Islamic State) or Ukraine?"
"Of course Ukraine," Patrushev replied. Asked about the remark later, he said there were "many" indications of Ukrainian involvement.
Senior Ukrainian presidential aide Mykhailo Podolyak dismissed the Russian claims as lies.
"The lies are officially spread by Patrushev, and after that by the head of the FSB Bortnikov," Podolyak said.
British Foreign Secretary David Cameron posted on X: "Russia’s claims about the West and Ukraine on the Crocus City Hall attack are utter nonsense."
The remarks by Patrushev and Bortnikov offer an insight into hawkish thinking at the top of the Kremlin elite. The FSB, the main successor to the Soviet-era KGB, is one of Russia's most powerful institutions.
The United States has intelligence confirming Islamic State's claim of responsibility for a deadly shooting at a concert near Moscow, two U.S. officials said on Friday.
U.S. National Security Council spokesperson Adrienne Watson said Washington earlier this month shared intelligence with Russia about a planned attack in Moscow.
Bortnikov, when asked about the information supplied by Washington, said it was not always very concrete information.
Putin said on Saturday in an address to the nation that all those responsible for the concert attack would be punished.
On Monday, he said for the first time that radical Islamists had carried out the attack but that the attackers were trying to flee to Ukraine, and he questioned why Islamists would want to attack Russia at this time without being nudged to by others.
"We know that the crime was carried out by the hand of radical Islamists with an ideology that the Muslim world has fought for centuries," Putin said. "We want to know who ordered it."