(CNN) -- Painted sky-blue, these small flying machines may look like toy planes but they have South Korea scrambling to secure its airspace. In recent weeks, South Korea's defense ministry has discovered three crashed unmanned aerial vehicles (UAVs) that it believes belong to Pyongyang. Equipped with Japanese-made digital cameras, the drones captured images of important military installations and South Korea's presidential office in Seoul, according to local media reports. South Korea says the aircraft are a sign of Pyongyang's heightened surveillance that should be taken seriously, and yet officials and experts suggest the drones pose little, if any, real threat.
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South Korea suspects that three drones discovered in recent weeks belong to North Korea
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The unmanned aircraft are fitted with digital cameras, difficult to detect with radar
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Experts say the drones are low-tech and pose little threat
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Seoul is bolstering its air defense network in light of the discovery
"Drones suspected of belonging to @placeholder appeared to have spied in all directions, but our military authorities were completely in the dark about this," she said.
Two days later, a spokesperson for the defense ministry told CNN that @placeholder plans to purchase low-altitude radar to improve the country's ability to detect small UAVs.