Russia authorities have said from the outset that they believe Ukraine was linked to the attack, even though Ukrainian officials have denied it and the militant group Islamic State (IS) has claimed responsibility.
In a statement, Russia's Investigative Committee said for the first time that it had uncovered proof of a Ukrainian connection.
While it described the nature of the alleged evidence, it did not publish it.
"As a result of working with detained terrorists, studying the technical devices seized from them and analysing information about financial transactions, evidence was obtained of their connection with Ukrainian nationalists," it said.
It said there was "confirmed data" that the attackers had received significant amounts of cash and cryptocurrency from Ukraine.
Another suspect involved in "the terrorists' financing scheme" had been detained, the committee said.
White House adviser John Kirby says talk of Ukrainian links to an attack in Russia are "nonsense". (AP PHOTO)
White House national security spokesman John Kirby described the Russian allegations as "nonsense and propaganda" and said IS was solely responsible for the attack.
"In fact, the United States tried to help prevent this terrorist attack and the Kremlin knows this," he said.
The United States had publicly warned earlier in March that it had intelligence that "extremists" were planning an imminent attack in Moscow.
Kirby said it had also provided written warning to Russian security services on March 7 at 11.15am.
Revealing the exact time of the alert appeared aimed at neutralising Russia's charges against Ukraine.
Three days before the attack, Putin dismissed foreign warnings of a potential extremist attack as "blackmail".
US officials say they believe it was Islamic State Khorasan, the network's Afghan branch, that was responsible for the concert shooting.
⚡� Russia's Investigative Committee:— MFA Russia 🇷🇺 (@mfa_russia) �� Interrogations of the detained [Crocus City Hall] terrorists, study of their technical devices & the analysis of information on their financial transactions point 👉 to their connections with Ukrainian nationalistshttps://t.co/lhKqa8HD1K pic.twitter.com/VsfcpMEfpQMarch 28, 2024
"We take seriously our duty to warn. We never want to see innocent lives lost in terrorist attacks," Kirby said, adding that the US has passed "many warnings" to Russai "about various threats" since September.
Russia says the fact that the US was able to name the alleged perpetrator so fast is suspicious.
Foreign security analysts say the attack raised questions about the resourcing and priorities of Russian intelligence agencies that have been heavily focused on the Ukraine war and the need to stamp out opposition to it within Russia.
Eleven people were arrested in the first 24 hours after last Friday's shooting and eight of these, including the four suspected gunmen, have been placed in pre-trial detention.
Seven are from Tajikistan and the other from Kyrgyzstan.
The four main suspects were allegedly under the influence of drugs when carrying out the mass shooting, according to a report by Russian state news agency TASS.
"Which drugs or psychotropic drugs they have consumed will be determined by an expert," TASS reported on Thursday, citing investigators.
