"We want to cooperate with the U.S. and other countries to stop the North from exporting small UAVs for fear that they could be used for terrorist attacks," a ministry spokesman said.

The ministry is analyzing their memory chips, which it believes contain map coordinates for their takeoff and landing. A joint South Korea-U.S. investigation team is embarking on a more detailed investigation.

Analysis of images retrieved from the UAVs' cameras showed that they took photos while flying over areas clustered with military installations, the ministry added.

Investigators determined that the drones are equipped with commercial components from six counties -- China, the Czech Republic, Japan, South Korea, Switzerland and the U.S. -- and include 4-mega DRAM memory chips from Samsung.

Three small unmanned aerial vehicles found in Paju, Gyeonggi Province, on Baeknyeong Island, and in Samcheok, Gangwon Province definitely came from North Korea, the Defense Ministry here confirmed Friday.

The UAVs are very similar to those unveiled during a parade marking regime founder Kim Il-sung's birthday in 2012 and shown during leader Kim Jong-un's visit to a military unit in 2013, in that they were painted identical sky blue with a pattern of white clouds.

The images taken by the UAV that crashed in Samcheok are impossible to restore because the man who found it in October last year took the memory chip from its camera and has since stored and erased his own images repeatedly.

The North has had the technology to make such drones since 2000 and it is highly likely that they have been mass-produced, according to the Agency for Defense Development.

Many broken parts of the UAVs discovered on Baeknyeong Island and in Samcheok had simply been repaired with gaffer tape.

The ministry described its findings as "circumstantial evidence." Decisive evidence will rely on the analysis of the UAVs' CPU memory chips.

It is possible that the North in some way made it difficult to analyze the memory chips because lot numbers or serial numbers on some parts such as transmitters were erased to make it difficult to trace the sources.

The head of the investigation said it will take another two weeks to a month to finish the analysis.

All the parts of the drones are easy to buy and their import and export are hard to control, the ministry added.

Once it is proven that the UAVs were made in the North, Seoul will protest against the infiltration through the UN Command and international organizations, since it regards it as a grave violation of the South Korean airspace.

