CNN has revealed rare footage of North Korean spies attempting to steal what they thought was top-secret missile plans. However, they were part of a complex sting operation carried out by the Ukrainian authorities to apprehend them.

The prison in Ukraine where the spies are being held

The prison in Ukraine where the spies are being held Photo Credit: CNN/Channel 2 News

Ukrainian footage providing a rare glimpse into the murky secret world of missile espionage was revealed by CNN on Thursday.

In the footage, which is from 2011, two North Korean spies are seen inside a half-lit Ukrainian warehouse taking photos of what they think is top-secret advanced missile designs. The two spies were sentenced to 8 years on espionage charges and are currently serving their sentence in a Ukrainian prison west of Kiev.

Watch: North Korean spies stealing Ukranian “missile designs”

The older of the two men, a man in his 50s from Pyongyang, is known to authorities as X5 and speaks Russian with a slight accent. His younger partner is known as X32 and is a technology expert.

The two are the only spies currently known to be in custody in Ukraine; however, Ukrainian sources said that they succeeded in foiling several North Korean attempts to obtain secret missile plans.

A senior Ukrainian security official who handled the case told CNN that Pyongyang cannot obtain Ukrainian missile technology and he is convinced that any attempts of doing so have been thus far foiled.

According to the official, two additional North Koreans who arrived in Ukraine from the North Korean embassy in Moscow were expelled after they were caught trying to obtain “missile munitions, homing missile devices in particular for air-to-air class missiles.” A third North Korean, whose task was to smuggle the system out of Ukraine, was caught and expelled as well.

Pyongyang's improved long-range missile

Pyongyang’s improved long-range missile Photo Credit: Reuters/Channel 2 News

As of 2015, a total of 5 North Koreans were expelled from Ukraine due to “assisting North Korea’s intelligence work in Ukraine,” according to the official.

Ukrainian security services provided the footage, along with details of the complex sting operation that was carried out to catch the two spies.

These revelations may have been made public in order to dispel recent claims according to which Pyongyang’s advancement in intercontinental missile technology was due to top-secret missile designs stolen from or given by the Ukrainian authorities.

Ukraine denied any connection with the North Korean long-range missile program and claimed the missile designs may have been provided by Russia, which in its turn also denied providing any assistance to North Korea.