Ukraine has jailed two North Koreans for eight years on charges of trying to obtain sensitive missile production data, a law enforcement official said on Monday.

The sentence was issued last month and came into force in recent days after officials decided not to extradite the two back to the Stalinist state, the official told AFP.

"They will serve their sentence in Ukraine," said the official.

The Segodnya daily said the two men had admitted guilt during the trial and that their lawyer had not appealed the sentence.

The agents worked under the cover of the North Korean trade mission in Minsk, capital of the neighbouring ex-Soviet republic of Belarus, the report said.

Ukraine has a vast defence industry and was an important part of the Soviet military industrial complex, producing many of the missiles and space technology used by Russia today.

Segodnya said the two spies tried to obtain data about liquid-fuelled engines and other secrets from Yuzhnoye, a designed bureau famous for coming up with the feared SS-18 intercontinental ballistic missile during the Cold War.

The two were arrested while trying to take photographs of sealed doctoral theses on secret missile engines in the eastern city of Dnipropetrovsk, the report said.