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. 

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.