“During 20 years of work in the Estonian security police service, Dressen obtained and delivered to Moscow a colossal amount of valuable documents regarding secret operations of the U.S. Central Intelligence Agency and the British MI6 against Russian Federation from the position of the Baltic countries”, he said.

Estonian Eston Kohver was handed over by the Russians in return for Alexei Dressen, also an Estonian, who was imprisoned in Estonia for spying in 2012.

Two border checkpoints were closed during the exchange, which took place on a bridge over the Piusa River that divides Russia’s western Pskov region and Estonia’s Polva county, according to a statement by Russia’s Federal Security Service (FSB).

Kohver’s defense lawyer, Mark Feigin, said that the swap was “organized on the political level” and was timed to improve Putin’s image before his appearance at the UN.

Kohver was sentenced to 15 years in jail on August 19 at a closed-door trial after being found guilty of espionage and illegally crossing the Russian border.

He had been arrested in 2012 along with his wife, Victoria Dressen, who was given a suspended sentence. “There are no other reasons”, Feigin wrote.

Putin is flying to New York to make a speech at the United Nations, for the first time in a decade, and to meet US President Barack Obama for their first formal talk since 2013. Estonia claimed he was abducted at gunpoint in Estonian territory in September previous year. “I would particularly like to thank the people who helped my family cope when I was gone”, Kohver said, during a news conference following his release.

“A wrong has been made right”, tweeted Swedish Foreign Minister Margot Wallstrom.

The apparent kidnapping of an official from a North Atlantic Treaty Organisation country has been seen by some commentators as a warning of Russia’s capabilities and intentions in the Baltic states, where tensions have risen since the outbreak of the Ukraine crisis in 2014. He was sentenced to 16 years in prison.

Exchanges of captured agents were a regular tactic across the Iron Curtain in the Cold War, sometimes on the Glienicke Bridge between East and West Germany.