The North Korean leader Kim Jong Un called for an increase in the production of “military nuclear material” and the construction of more powerful weapons, state media reported.

This latest threat from Kim, who has previously called for an “exponential” increase in his country’s nuclear weapons production, came shortly before the arrival of US aircraft carriers in South Korea.

The North Korean leader said his country should prepare to use its nuclear weapons “anywhere and anytime,” according to the official KCNA news agency.

At the same time, he asked the officials “to develop the production of military nuclear material in the long term in order to implement the plan (…) of the exponential increase of nuclear arsenals”.

It also “encouraged the continued production of powerful nuclear weapons,” KCNA added.

When North Korea has “perfected” its nuclear weapons systems, “the enemy will fear us and will not dare to challenge the sovereignty of our state, our system and our people,” Kim said.

Last year, North Korea announced that its status as a nuclear power is “non-negotiable”. In early March, Kim asked the country’s military to step up its military training ahead of a “real war.”

Today North Korea’s military said it had conducted a second test of a “nuclear-powered, underwater attack drone”, following a first test last week.

The test of this new weapon, called Haeil, which means tsunami in Korean, was in response to the recent joint US-South Korean military drills, the largest in five years.

The drone traveled underwater “for 41 hours and 27 minutes traveling 600 kilometers” before hitting a target off Hamgyong province early Monday morning, KCNA reported.

At the same time, on the same day, the North Korean military carried out a simulated nuclear attack with tactical ballistic missiles.