A German court on Tuesday convicted a married couple of spying for Russia over more than two decades and handed them prison sentences for passing European Union and NATO secrets to Moscow.

Andreas and Heidrun Anschlag — known only by the fake names on the Austrian passports they used to enter Germany — were sentenced to 6 ½ years and 5 ½ years in prison, respectively, by the state court in Stuttgart. The court said their real identity hasn't been established, but they are believed to be Russian and in their early to mid-50s.

The verdict came after a court in the Netherlands sentenced a Dutch diplomat in April to 12 years in prison for delivering EU and NATO documents to the agents. The Anschlags sent on the information he gathered — in exchange for bribes of at least 72,200 euros ($94,000) — to Russia's intelligence agency, judges said.

The German judges determined that the documents were confidential rather than top-secret and found no evidence of "concretely measurable damage" to Germany, the Netherlands, the EU or NATO. But while the Anschlags' sentences fell short of the maximum possible 10 years for espionage, the court found that their actions "significantly endangered confidence in the reliability and ability to protect secrets" of Germany and its partners.

The couple's activities — including dead letter drops and radio communications with Russia — sounded like something out of the Cold War, but the case centered to a large extent on their actions in the final years before their arrest in 2011.

Andreas Anschlag arrived in what was then West Germany in 1988, the year before the fall of the Berlin Wall. Heidrun arrived in 1990, the year Germany was reunified. Both claimed to be Austrian citizens of South American background and blended into German society, living in four provincial German towns over the next two decades.

The two were arrested in October 2011 — investigators arrived at their home just as Heidrun Anschlag was receiving a radio message from Russia, the court said. Authorities were able to piece together fragments of their communication with Moscow from computers that they seized, but the court said it wasn't possible to establish exactly how many documents from the Netherlands the couple handed over.

The defendants declined to testify during the trial, which opened in January. A lawyer for Andreas Anschlag, Horst Dieter Poetschke, said the verdict was "acceptable" but the defense would consider whether to lodge an appeal.

The Dutch diplomat already convicted in the case, Raymond Poeteray, was arrested in March 2012. He has appealed against his conviction.

German media have reported that there were three-way talks involving Germany, Russia and the United States about a possible spy swap. The Russian Foreign Ministry and U.S. Justice Department have declined in the past to comment on the case.