The criminal group was found guilty of killing five business and administration executives. The gang operated from 1992 and comprised over 20 members, mainly residents from the Leningrad Region and Moscow.
The court's decision followed a unanimous guilty verdict by the jury on February 27.
During the trial, one of the defendants completely and two others partially admitted their guilt.
The investigation continues to seek other gang members and those responsible for ordering the murders.
Investigators suspect Alexander Pumane was also involved in the crimes. Former submarine officer and St. Petersburg resident, Pumane was detained in Moscow in September 2004 while driving a car containing explosives.
Pumane died in hospital the next day after being seriously injured during interrogation. Two police officers were consequently found guilty of inflicting fatal injuries on Pumane during interrogation by a Moscow court.
