Four men accused of involvement in the Moscow concert hall attack that claimed the lives of more than 137 people were charged with terrorism on Monday and ordered to be detained pending trial. 

All four risk a life sentence in prison, a statement from Moscow's Basmanny district court said.

The men were to be held until May 22, but that could be extended depending on when the date for their trial is set. 

According to the statement, the court said two defendants had pleaded guilty, and one from Tajikistan, "entirely acknowledged his guilt." On that note, officials have already said the gunmen were all foreign nationals.

Russian officials reported that 11 were arrested in connection with the terrorist attack on Friday at the Crocus City Hall in Moscow's northern suburb of Krasnogorsk, including four who carried out the killings.

The court released footage of three suspects being brought to a courtroom handcuffed and bent double by police officers. They were seated in a glass-fronted cell reserved for defendants.

Earlier on Saturday, a man apprehended in connection with the fatal terrorist attack at the Crocus City Hall near Moscow admitted that he opened fire on individuals at the concert venue in exchange for money.

The suspect confessed during an interrogation session captured on video and shared on Telegram by Margarita Simonyan, the editor-in-chief of RT and the Rossiya Segodnya media group, that he shot "people at Crocus ... for money." 

The individual detailed that approximately a month prior, he was contacted via Telegram by an unidentified individual who subsequently provided him with weapons. He further disclosed that his decision to carry out the terrorist attack was influenced by a conversation with an associate of a "preacher".

The suspect admitted that his handlers had instructed him to eliminate all individuals present at the concert venue. Additionally, in the video footage, the detainee verified that he had entered Russia from Turkey on March 4.