Police found DNA matching that of the fugitives of the disbanded Red Army Faction (RAF) at the scene of a botched armed robbery last June, and prosecutors also linked the three to a similar attack last December.
Two men and one woman have been wanted for decades as members of the anti-capitalist RAF, also known as the Baader-Meinhof Gang, which rocked Germany with a wave of bombings, killings and kidnappings targeting political and business leaders from the 1970s to the early 1990s.
Last year, according to prosecutors, they were apparently at it again, starting with a failed robbery on June 6.
In the attack, three masked assailants armed with two AK-47s and a grenade-launcher opened fire on a money van near the northern city of Bremen.
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Police said the attackers used a vehicle to block the security van that was carrying about one million euros and may have used a jamming device to disable the mobile phone communications of the two guards.
"There is no evidence to suggest... A terrorist background," said the Lower Saxony state prosecutors about the June attack.
"Rather it must be presumed the crime aimed to help finance their underground lives."
There was also "suspicion because of fresh results of investigations" that the three were involved in a third attack on a cash transporter, last December 28 in the central city of Wolfsburg, said federal prosecutors in Karlsruhe.
"There are parallels in the execution of the crime and the evidence," Wolfsburg prosecution spokesman Klaus Ziehe told AFP, adding that DNA checks were ongoing.
The group, which had links to Middle Eastern militant organisations, declared itself disbanded in 1998.
Staub, Garweg and Klette, alleged member's of the RAF's so-called "third generation", have long been wanted as chief suspect in a 1993 explosives attack against a prison under construction in Hesse state.
In the attack, five RAF members climbed the prison walls, tied up and took away the guards in a van, then returned to set off explosions that caused about 600,000 euros worth of property damage, said prosecutors.