The ministry said he had been released two weeks early for work he performed in prison but provided no information about where Klar would serve his five years of parole during which he must regulalry report to the police.
Heinz-Juergen Schneider, Klar's lawyer, said his client would not be appearing on television talk shows or giving interviews.
Schneider, who said Klar was "pleased" to be out of prison at last, said: "He is going to decide himself what he will be doing and where."
The planned release of Klar had stirred controversy in Germany after Horst Koehler, Germany's president, considered a request to pardon him last year.
At the time, some politicians said the killer had done his time and no longer posed a threat to society.
Others argued that Klar had never shown regret for his actions or offered details on the killings and deserved no pardon.
The Red Army Faction, also known as the Baader-Meinhof Gang after founders Andreas Baader and Ulrike Meinhof, was an extreme leftist group which grew out of student protests and anti-Vietnam War movements in 1960s West Germany.
Its members launched violent attacks to combat "US imperialism" and against what they said was a morally corrupt society that had failed to deal with its Nazi past.
The Red Army Faction is believed to have killed 34 people between 1970 and 1991, before disbanding 10 years ago.
Among the murders Klar was convicted of being involved in were those of Siegfried Buback, a federal prosecutor, and Juergen Ponto, the head of Dresdner Bank, both killed in attacks leading up to the bloody German Autumn of 1977.
Michael Buback, Buback's son, called on Klar to name the masked assailant who murdered his father.
Klar was convicted as party to the murder, but the son said he worried that the assailants might be people who had completely escaped punishment and were being protected by Klar's silence.
'Brutal, inhumane man'
Joerg Schleyer, son of Hanns Martin Schleyer, an industrialist murdered in 1977, said: "I wouldn't believe a show of remorse from such a brutal, inhumane man."
Schleyer said the group had been common criminals, not political opponents.
"That also means you cannot deny them the benefits that the rule of law grants any criminal," he said.
A feature film released this year, The Baader-Meinhof Complex, depicts some of the murders and robberies carried out by the group.
Germany's film export board has nominated it for a best-foreign-film Oscar.