South Korea's military confirmed that it had test-fired a solid-fueled rocket on Friday after the unannounced launch led to rumors about a UFO or a North Korean missile launch.
In a statement, the Defense Ministry said that the launch was part of an initiative to build a space-based surveillance capability and fortify the country's defense posture.
The department said it did not flag the public about the launch in advance because it involved sensitive military security issues.
A light trail was captured in an image from Goyang that evening, sending social media sites into a frenzy.
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"What is this? Is this a UFO? I’m scared," said one Twitter user.
Others suspected a less sinister or supernatural phenomenon: a drone or light show.
According to local media emergency offices and authorities received hundreds of reports of witnessing a suspicious unidentified flying object.
In March, South Korea conducted its first successful launch of a solid-fuel rocket.
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The Defense Ministry said Friday's launch was a follow-up.
The launch came just days after South Korea accused North Korea of flying five drones across the border on Monday for the first time in five years.
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South Korea’s military detected the drones but failed to shoot them down, forcing the military to apologize for that later.
The Associated Press contributed to this report.