Two North Korean nationals were sentenced to eight year prison terms after being caught trying to steal secret rocket technology from the Ukraine, local sources said Saturday.

Sources said the North Koreans identified as Ryu Song-chul and Lee Tae-kil were arrested for spying in July after they tried to steal classified technology from the Yuzhnoye Design Bureau in Dnipropetrovsk. The sentence was handed down by a Ukrainian court late last month.

Yuzhnoye's Dnipropetrovsk bureau is in charge of rocket and satellite development and was responsible for making the 11,000-kilometer range R-36M multi-warhead intercontinental ballistic missile during the Soviet era.

Security Service of Ukraine, which carried out the arrest, said the two worked at North Korea's trade representative office in Minsk, Belarus, but had made contact with a researcher at Yuzhnoye.

It said the researcher had notified authorities of the contact and helped set up a trap where the two were apprehended as they took photos of the classified data.

The technology that the two North Korean sought was centered on rocket vehicles and in particular liquid fuel engine systems that could greatly increase the range of a rocket.

Local experts said that if Pyongyang secured the technology, it would have helped them build rockets that could reach the continental United States.

The source, meanwhile, said that the two men claimed they were innocent of all charges and planned to appeal the case to a higher court.

North Korea conducted two nuclear tests in 2006 and 2009, and has launched several long-range rockets, most recently its failed rocket launch on April 13. It has claimed its rocket program is to place a satellite into orbit but the international community has condemned it as an attempt to skirt international regulations while testing ballistic missile technology.