Kim praised the workers there, encouraging them to continue their production to boost the country's economy and national defense capabilities, according to JoongAng Ilbo.
The Korea Central News Agency also published pictures of a massive public rally and fireworks that took place Friday.
Meanwhile, U.S. National Security Adviser H.R. McMaster said the likelihood of war between the United States and North Korea is increasing every day.
Following North Korea's Hwasong-15 intercontinental ballistic missile test last week, McMaster told Fox News on Saturday, "The greatest immediate threat to the United States and to the world is the threat posed by the rogue regime in North Korea."
He added that, through trial and error, the regime's nuclear and missile capacity has been increasing over time, and stressed that "time is running out" in terms of resolving the North Korea problem.
Pyongyang claimed that the Hwasong-15 missile was "the most powerful ICBM" launched, capable of targeting the any part of the U.S. mainland.
Analysis of the missile flight is still ongoing, according to a U.S. official interviewed by CNN on Saturday, but experts believe that the ICBM broke apart as it re-entered the Earth's atmosphere.
U.S. and South Korean analysts doubt that North Korea has mastered critical technologies required to launch and direct a missile and ensure its survival upon re-entry.
To bring a nuclear warhead back through the atmosphere, the ICBM would have to endure scorching temperatures of 6,000 to 7,000 degrees, SBS reported.
However, experts have noted significant efforts to improve re-entry capability with the latest ICBM sporting a blunt and rounded warhead, unlike the sharp tips of the Hwasong-14 ICBM tested in July, Hankyoreh reported.