Looks like they had bombings even in Soviet Union, back at the peaceful and quite 1970s. That times when anything anti-Soviet was banned, and people couldn't gather in groups larger than three of participants for the reasons different than praising Soviet regime it looks rather surrealistic and unreal, but still there were some. Day of January 8th, 1977 had three of those happened almost at once in the Soviet capital, the Moscow city. One was in the subway (maybe that was the first of the subway bombings
ever) and other too happened in the grocery store and in a residential complex. Seven were killed and more than thirty wounded. The authorities didn't succeed too much in catching the suspects, and as a matter of a fact didn't have reasons to suspect anyone neither enough evidences to build up any sane versions of who could do this. No any groups took the responsibility too, in reality there were no any groups operating in Soviet Union before this accident.