The convicts were members of the so-called Kingisepp criminal group, named after a town in northwest Russia, which operated from 1992 and comprised over 20 members, mainly residents from the Leningrad Region and Moscow.
The court determined that Yury Vasilyev and Denis Pinchuk were involved in the mining of the door of a regional prosecutor's office, which caused no victims but damaged property, and of attempting to murder another member of their gang in 2002.
Vasilyev, who was also found guilty of illegal production, transportation and possession of explosives, was given nine and a half years.
"The court considered mitigating circumstances - that the convicts are fathers of small children and surrendered to police," the verdict says.
Both men admitted their guilt.
In March, a Moscow court sentenced seven other members of the gang to prison terms of between 13 and 19 years for homicide and attempted murder.
They were found guilty of killing five business and administration executives.
Investigators suspect that Alexander Pumane was also involved in the crimes. A former submarine officer and St. Petersburg resident, Pumane was detained in Moscow in September 2004 while driving a car containing explosives.
Pumane died in the hospital the next day after being seriously injured during interrogation. Two police officers were subsequently found guilty by a Moscow court of inflicting the fatal injuries on Pumane during their interrogation of him.
