North Korea sharply criticized South Korea’s plan to build its first nuclear-powered submarine on Tuesday, calling the move a “grave development” that risks triggering an uncontrollable “nuclear domino” across the region.

In a 3,800-character commentary, the state-run Korean Central News Agency (KCNA) said Seoul’s newly approved nuclear submarine program would “destabilize the military and security landscape of the Korean Peninsula and beyond” and represents a step toward South Korea weaponizing nuclear energy.

“The ROK’s possession of a nuclear submarine is a strategic move for ‘its own nuclear weaponization’ and this is bound to cause a ‘nuclear domino phenomenon’