Russia is planning a "large scale trial" for the ISIS-K terrorists that attacked Moscow's Crocus City Hall on Friday, according to reports

       Four gunmen and 11 operatives in total were involved in the attack that saw at least 133 people killed after the attackers stormed into the venue and opened fire.

       Images also showed the outside of the venue on fire, which was reportedly started when the terrorists threw some kind of incendiary device.

       Russian President Vladimir Putin has vowed revenge for the attack while also suggesting the attackers tried to flee toward Ukraine.

       He said: “We will identify and punish everyone who was behind the terrorist attack, who prepared this strike against Russia and its people.

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       "ISIS bears sole responsibility for this attack. There was no Ukrainian involvement whatsoever."

       Reporting from outside the Crocus City Hall in Moscow, Al Jazeera’s Yulia Shapavalova cited sources who reportedly said a trial is being prepared for the attackers.

       She said: “Moscow’s Basmanny court is preparing for a large-scale trial in the near future”, adding that the attackers may be brought there.

       She also described the scenes outside the venue,

       Shapavalova said: “We can see flags raised to half-staff on the Russian house of parliament and other buildings. People are shocked, they’re grieving… there are numerous memorials throughout Russia.

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       “The clearance of the rubble continues with rescue dogs looking for people under the rubble… the death toll could rise. Today, the whole day is to be devoted to search and rescue, after which the main part of the operation will mostly be completed.”

       While Putin has attempted to blame Ukraine for the attack, the US has said Kyiv was not involved.

       National Security Council spokesperson Adrienne Watson said: "ISIS bears sole responsibility for this attack. There was no Ukrainian involvement whatsoever."

       Following the attack, footage has emerged of one suspect purportedly being interrogated by law enforcement agents.

       Footage shared by the RIA Novosti news agency showed the man lying on the ground while being quizzed on how he made his way to Russia.