The suspects, identified as Andreas and Heidrun Anschlag, were reportedly caught red-handed in the town of Marburg listening to encrypted radio messages from Moscow, The Moscow Times reported Tuesday.
Espionage experts said working with encrypted radio messages was risky and low-tech in an age when the Internet offers intelligence agencies easier and more secure communications.
The suspects are accused of operating in a manner similar to the 10 sleeper agents discovered and arrested in the United States last year, and to have maintained contacts with one of them, the red-haired Anna Chapman, The Moscow Times reported Tuesday.
Chapman has become a national celebrity since returning to Russia in a prisoner swap.
Authorities allege the couple operated in Germany for more than 20 years after moving there in 1990 by way of Mexico using false Austrian passports.
But an unidentified official in Russia's Foreign Intelligence Service told the Moscow newspaper Izvestia the couple were part of a group that had effectively retired from the agency.
Such agents are normally left alone because they have "residency permits, pension rights and families," the official said.
Experts said the affair only showed that Russia's intelligence service was holding on to outdated methods.
Texas principal bans speaking Spanish, stirs controversy
Exploding whale video goes viral on Internet