Shootings, explosions and a fire at a concert hall Friday evening that left dozens dead in Russia are being investigated as a terrorist attack, the country’s top investigative agency said. 

Russia’s Federal Security Service said more than 60 people were killed in the attack at Crocus City Hall, a music venue, and nearly 150 others were injured in one of the deadliest attacks in the country in years. 

The attack began when gunmen donning combat gear burst into a Moscow-area concert and opened fire. 

Concertgoers, who had gathered in the hall to see the Russian band Picnic, were being evacuated, but some remained trapped inside the burning building, Russian media said. 

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A Russian Rosguardia (National Guard) service member secures an area as a massive blaze is seen over the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide.  (AP Photo/Dmitry Serebryakov)

The gunmen also threw explosives inside the concert hall during the attack, which set the building on fire, Russian media reported.  

Russia’s Investigative Committee said it has opened a criminal probe into the attack but hasn’t said who might be behind it. 

Russian Culture Ministry has canceled all mass and entertainment events in the coming days in the area. 

Videos from inside the venue showed the armed assailants shooting as they walked inside the lobby.  

A massive blaze is seen over the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide.  (Sergei Vedyashkin/Moscow News Agency via AP)

Moscow Mayor Sergei Sobyanin called the attack a «huge tragedy.» 

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Former Russian president and current Deputy Chair of the Security Council of the Russian Federation Dmitry Medvedev wrote on Telegram that if «Moscow finds the perpetrators of the attack were connected with the ‘Kiev regime’ then all [Ukrainians] should be found and destroyed…including state officials. If it is established that these are terrorists of the Kyiv regime, it is impossible to deal with them and their ideological inspirers differently. All of them must be found and mercilessly destroyed as terrorists. Including officials of the state that committed such atrocity.» 

The attack comes on the heels of Russian President Vladimir Putin’s landslide reelection and amid its war in Ukraine, just more than two years after Moscow invaded the country. 

«At this time there are no intelligence indicators that the attack was orchestrated by Russian intelligence services as a pretext to take out Ukraine leaders,» Rebekah Koffler, a strategic military intelligence analyst and the author of «Putin’s Playbook,» told Fox News Digital. 

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She continued, «Putin doesn’t need such a pretext because targeted assassinations are permitted under the Russian federal law, ‘On Countering Extreme Activity,’ that was approved by Putin in 2002, two and a half years after he assumed the presidency, and updated in 2006. This law already allows Russian intelligence services to «eliminate» (likvidirovat’) [Ukrainian President Volodymyr] Zelenskyy and other military and political leaders of Ukraine as ‘persons presenting a threat to the Russian state.’» 

A massive blaze is seen over the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landlside.  (Sergei Vedyashkin/Moscow News Agency via AP)

She added, «Whether Ukrainian special services are behind the attack or not, the Russians may very well conduct disinformation operations to blame Ukraine and the West for the attacks. Not necessarily for retaliation purposes (they don’t need to – because Russian offensive campaign in Ukraine is going as planned, as far as Putin’s assessment). But in order to continue rallying the Russian people behind Putin, supporting his war in Ukraine, and to continue feeding the anti-Western sentiment among the Russians, to justify additional defense spending, additional recruitment of troops, etc.»

Koffler said she didn’t have final analysis on who is behind the attacks yet. 

Zelenskyy has denied any Ukrainian involvement. 

«Ukraine certainly has nothing to do with the shooting/explosions in the Crocus City Hall (Moscow Region, Russia). It makes no sense whatsoever,» he said on social media, adding, in part, «there is not the slightest doubt that the events in the Moscow suburbs will contribute to a sharp increase in military propaganda, accelerated militarization, expanded mobilization, and, ultimately, the scaling up of the war. And also to justify manifest genocidal strikes against the civilian population of Ukraine.» 

On March 7, the U.S. Embassy in Russia warned against «imminent plans» for an attack by extremists.» 

«The Embassy is monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts, and U.S. citizens should be advised to avoid large gatherings over the next 48 hours,» the embassy said two weeks ago. 

The warning came after Russian authorities said they had stopped an attack by Islamic State extremists planned at a mosque in Russia. 

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Fox contributor Dan Hoffman, a former CIA station chief in Moscow, told Fox News normally a warning like the U.S. embassy’s would be «based on intelligence» that could be «fragmentary.» 

The Associated Press and Reuters contributed to this report.