The 1977 Moscow bombings were a series of three terrorist bombings in Moscow on 8 January 1977. The attacks killed seven people and seriously injured 37 others. While no one claimed responsibility for the bombings, three members of an Armenian nationalist organization were executed in 1979 after a KGB investigation and a secret trial. Some claimed these were not the real culprits. Andrei Sakharov issued a public appeal, expressing concern the bombings might have been a ‘provocation’ by the security organs.
Source: ‘1977 Moscow bombings,’ Wikipedia