Russia has released two Lithuanians and one Norwegian versus two Russians held in Lithuania in a Cold War-style "spy swap" that puts an end to a number of high-profile espionage cases.

Russian authorities released Lithuanians Yevgeny Mataitis and Aristidas Tamusites, who were sentenced to 13 and 12 years in prison respectively in Russia for spying in 2016.

The Russian news agency TASS reported that Mataitis, who also holds Russian citizenship, was passing secret military information while serving in the Russian armed forces when he was a captain.

Norwegian Frude Berg, a retired border guard, was arrested in Moscow in 2017 and convicted of collecting information for Norway but pleaded not guilty.

Norwegian Prime Minister Erna Solberg told a news conference she had spoken to Berg by telephone and would return home as soon as possible. "We are delighted that Freudie Berg will return home as a free man."

Solberg said Lithuanian President Gitanas Nusida and his country's parliament reflected "the spirit of a great ally and a true friend, and we will continue to be grateful."

Cross-border swap
The swap was carried out midday on Friday at a Lithuanian site on the border with Russia's Kaliningrad enclave.

Norway and Lithuania are partners in the North Atlantic Treaty Organization (NATO), and Norwegian soldiers are participating in regular NATO exercises in Lithuania out of concern about Russian "hostility".

One of the released Russians is Nikolai Filipchenko, who was sentenced to 10 years in prison in Lithuania in 2017 for espionage.

Lithuanian media reported that Filipchenko was a lieutenant colonel in the Russian Federal Security Service and tried to recruit the personal guard of the Lithuanian president in order to eavesdrop on the presidential office.

Lithuanian prosecutor Sergei Moisenko, who was sentenced in 2017 to 10 and a half years in prison for espionage and illegal possession of weapons, said the Lithuanian prosecutor's office.

Lithuanian media reports said the Russians tried to gather information about the armed forces in Lithuania and NATO forces in the country.