Russian President Vladimir Putin urged attorneys Tuesday to do everything necessary so that the perpetrators of a massacre last week at a concert hall in the Moscow region will be punished.
Putin said investigators are establishing the circumstances of what happened.
"They (investigators) are uncovering details, determine the role and degree of guilt of each participant, study the conclusions of criminologists and experts," he said at a meeting at the General Attorney's Office board in Moscow.
The National Anti-Terrorist Committee is coordinating the work of different intelligence services that are engaged in the investigation, he said.
"I hope that the attorneys, within the limits of their powers, including at the presentation of state charges and during the trial, will do everything necessary to ensure that the criminals are fairly punished, as required by Russian law," he emphasized.
At least 139 people were killed and more than 180 injured March 22 when gunmen opened fire at Crocus City Hall in Krasnogorsk, Moscow Oblast.
The Investigative Committee said it detained 11 people, including four perpetrators, in the border region of Bryansk, who were on their way to Ukraine.
Moscow's Basmanny district court late Sunday charged the four perpetrators with terrorism and approved their pre-trial detentions until May 22.
