North Korea may be gearing up for a fifth nuclear test, given renewed plutonium processing activities at its nuclear test site, according to a Japanese media outlet.

Pyongyang`s Atomic Energy Institute said in a written interview with Japan`s Kyodo News Agency published earlier Wednesday that North Korea has "reprocessed spent nuclear fuel rods removed from a graphite-moderated reactor." The institute oversees North Korea’s main Yongbyon nuclear facilities.

It marked the first time the communist nation has confirmed resumption of plutonium production since the announcement of restarting of its Yongbyon nuclear reactor in 2013.

Plutonium’s critical mass to sustain a chain reaction is lower than that of enriched uranium, making it easier to produce smaller nuclear warheads.

The institute said also said that North Korea has been producing highly enriched uranium needed to produce nuclear weapons and power generation as scheduled." It also claimed the country has already succeeded in making lighter, minimizing and diversifying nuclear weapons. But it stopped short of revealing the amount of plutonium or enriched uranium North Korea has produced.

The institute said it will not halt its nuclear tests as long as Washington continues to pose a threat to the country. It also said the country will build a 100,000-kilowatt light-water nuclear reactor for experimental use to meet electricity demand.

If the resumption of nuclear fuel reprocessing for plutonium production is true, it means the North nullifies a deal reached in six-party denuclearization talks and it will be able to make more nuclear weapons, the news media reported.

North Korea in March was slapped with toughest-yet sanctions by the United Nations Security Council since it carried out the fourth nuclear test in January. It has not stop provocations, testing long-range ballistic missile and claiming to have miniaturized and sophisticated warheads capable of fitting into missiles that can reach as far as U.S. mainland.

By Hwang Hyung-gyu and Ahn Doo-won

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