A Dutch court jailed a former foreign ministry worker for 12 years on Tuesday for passing hundreds of sensitive military documents to Russia, including on NATO's activities in Afghanistan and Libya.

"The court rules as proven that he passed confidential documents to the Russian Federation for years at the request of the Russian intelligence service (SVR)," the court in The Hague said in a statement.

The 61-year-old spy, Raymond Valentino Poeteray, "perturbed and undermined the interests of the Netherlands and its allies," the court said.

"There were state secrets in some of the documents and the Netherlands' and its allies' interests were endangered," it added.

"He acted purely out of financial interest, to pay off his debts and allow him a certain lifestyle," it said, earning him 72,200 euros ($93,000) between January 2009 and August 2011.

The documents mainly concerned political and military matters in the European Union and NATO, including on the situation in Libya, the EU observer mission to Russia's neighbour Georgia, and missions in Kosovo and Afghanistan.

"The damage done to the European Union and NATO should be considered substantial," the court said.

Prosecutors had asked for a 15-year prison sentence.

The consular worker was arrested at Amsterdam's Schiphol airport a year ago as he was about to board a plane to Bangkok.

At the time of his arrest, law enforcement officials found four USB sticks containing sensitive information in a glasses case.

Prosecutors said he had booked a flight via Vienna so he could hand over the USB sticks.

The spotlight fell on the Dutch suspect after German police raided the home of a married Russian couple living in the central city of Marburg, allegedly the Dutch spy's handlers.

The pair, identified only by their codenames Andreas and Heidrun Anschlag, are accused of having been planted in West Germany from 1988 by the Soviet Union's KGB and later used by its successor secret service abroad, the SVR.

They are currently on trial in Stuttgart and could face up to 10 years in prison if found guilty of espionage.

German intelligence services tipped off the Dutch, who then launched a probe into Poeteray. German prosecutors said he had been handing confidential information to the couple since September 2008 under the codename "BR".

German domestic intelligence services in turn were tipped off about the couple after the FBI uncovered a Russian spy ring which included the highly publicised case of glamorous spy suspect Anna Chapman, who was deported from the United States in 2010.

Poeteray, who has worked for Dutch Foreign Affairs since 1978, pleaded not guilty to the charges and declined to testify during his trial.

His lawyer said he only wanted to help the couple find a home in the scenic southern province of Zeeland.

"The suspect belongs to a (small) group of spies whose long-term operational activities undermines and disrupts the interests of the Dutch state," the court said.