North Korean leader Kim Jong Un has warned that his country would not hesitate to use nuclear weapons if any force is used to violate its sovereignty.

The country's state-run Korean Central News Agency reported on Friday that Kim inspected a training base of army special operation units on Wednesday.

It showed photos of soldiers emerging from underwater with rifles and storming a building.

The report says Kim criticized a speech by South Korean President Yoon Suk-yeol that was made at a military ceremony on Tuesday. Yoon had said that if the North attempts to use nuclear weapons, it would face the end of its regime.

Kim said Yoon's remark acknowledges that the South Korea-US alliance is responsible for destroying regional security and peace.

The report says Kim threatened that "'if' the enemy, seized with extreme foolishness and recklessness," disregards warnings and attempts to use armed forces to encroach on the country's sovereignty, Pyongyang "would use without hesitation all the offensive forces it has possessed, including nuclear weapons."

A South Korean expert says Kim made the remarks to reaffirm Pyongyang's hostility toward Seoul ahead of the Supreme People's Assembly scheduled for Monday.

North Korea is expected to revise the country's Constitution during the assembly to officially designate South Korea as the "No.1 hostile nation."