South Korea is in discussions with its allies on how to counteract North Korea's claimed resumption of weapons-grade plutonium production, a government official said Thursday.

On Wednesday, Japan's Kyodo News reported North Korea had restarted its plutonium production for nuclear weapons use, citing its interview with Pyongyang's Atomic Energy Institute.

The North Korean institute said producing highly enriched uranium is necessary for nuclear weapons and power, highlighting that it has no plans to stop nuclear tests.

"If North Korea's claims are true, it's a violation of United Nations Security Council resolutions," the government official said, asking not to be named.

"Discussion with allies on ways to respond has been started," the official said, alluding to possible punitive actions by the UNSC.

Reversing an agreement to suspend uranium enrichment at its 5-megawatt reactor in Yongbyon, Pyongyang declared it had restarted the reprocessing facility amid escalating tensions with South Korea.

The Wednesday report marks the first time North Korea has confirmed plutonium production since 2013, although international institutions and the U.N. nuclear watchdog, the International Atomic Energy Agency, have detected signs of operations at Yongbyon.

In reaction to the latest news report, South Korea's foreign ministry said a day earlier that it will "closely cooperate with relevant countries and the international community over how to respond to North Korea's move." (Yonhap)