The Red Army Faction, which was also known as the 'Baader-Meinhof gang' after founders Andreas Baader and Ulrike Meinhof, was an extreme left-wing movement which grew out of the student protests and anti-Vietnam war movements in the west Germany of the late 1960s.
The group is believed to have killed 34 people between 1970 and 1991, before disbanding ten years ago.
Request for pardon
Klar's case triggered a heated debate last year when Horst Koehler, Germany's president, considered a request to pardon him.
The debate pitted politicians who said the killer had done his time and no longer posed a threat to society against those who argued that a murderer who had never showed regret for his actions deserved no pardon.
Klar has been in prison since 1982 and was convicted in 1985 of nine murders and 11 counts of attempted murder.
Among the killings he was convicted of being involved in were those of Hanns Martin Schleyer, the chief of Germany's employers' federation, and Juergen Ponto, the head of Dresdner bank, both killed during the bloody 'German autumn' of 1977.
The role of the Red Army Faction has sparked both horror and fascination in Germany and inspired dozens of books and documentaries.
This year's film, The Baader Meinhof Complex, proved a box office hit in Germany and has been picked as an entry for best foreign language film at the 2009 Academy Awards.