BERLIN (AP) -- Dead letter drops. Fake papers with cover stories to match. Secret orders by radio from Moscow.
The accusations read like something out of the Cold War but the charges against a couple who went on trial Tuesday in the German city of Stuttgart stem primarily from the decades after the 1989 fall of the Berlin Wall.
Andreas and Heidrun Anschlag -- only the fake names on the fake Austrian passports they used to enter Germany are known -- are charged with giving Russia's foreign intelligence service information on German, EU and NATO security policies and more general details on Russian-German relations.
The pair, thought to be in their 40s or 50s, denied the espionage charges in Stuttgart state court but refused to make any other statements Tuesday.
German officials won't divulge details other than those in the indictment, but the Der Spiegel magazine reported that the same U.S. mole in the Russian intelligence service who tipped off the FBI about a ring of sleeper spies based in the U.S. also divulged the existence of the couple in Germany. The information from Col. Alexander Poteyev, who Moscow convicted in absentia last year of high treason and desertion, was then passed along to German intelligence officials, Spiegel reported.
The Russian Foreign Ministry in Moscow and U.S. Justice Department spokesman Dean Boyd in Washington both declined to comment on the case.
Like the U.S. cell, Andreas and Heidrun Anschlag were able to work comfortably in a Western culture and pass unnoticed.
According to the indictment, Andreas arrived in 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, prosecutors said.
"With this backstory, underpinned by false Austrian passports, they built a normal existence within society to disguise their intelligence-gathering operations," prosecutors said.
They were charged with spying over 20 years until their arrest in October 2011. Prosecutors said between October 2008 and August 2011 the two were in contact with a third agent, who provided them with documents about EU and NATO operations from the Netherlands.
A Dutch Foreign Ministry employee, whose name has not been released, was arrested last March on suspicion of being the contact person who stole the information. The employee is due to go on trial there later this month.
Andreas Anschlag then passed the information on to the SVR -- the main successor to Russia's KGB -- using secret drop-off locations, known as dead letter boxes, prosecutors alleged. It was not clear how sensitive the stolen material was, although the Dutch employee has been charged with "preparing to spread state secrets."
"During the duration of their intelligence activities, the accused were in regular contact with their handlers," prosecutors said in their indictment. "Their instructions were received mainly through a special agents' radio. Their reports were transmitted to the intelligence via satellite. They also used an Internet video portal for hidden messages."
For their work, the couple received at least €100,000 ($135,000) a year in recent years, prosecutors said. If convicted, they could face up to 10 years in prison each.
A German federal agent will testify at the next court session.
Associated Press writers Michael Corder in The Hague, Nataliya Vasilyeva in Moscow and Pete Yost in Washington contributed to this report.