North Korean leader Kim Jong Un once again reiterated the threat to use nuclear weapons against South Korea and the United States, if attacked, state news agency KCNA reported on Tuesday.

Speaking at a defense university named after him on Monday, Kim also announced plans to accelerate North Korea's military growth, including its nuclear capabilities.

This comes just days after the North Korean leader vowed to use nuclear weapons against South Korea "without hesitation" if his country's sovereignty were threatened.

Kim decries South Korea-US alliance

Kim criticized South Korean President Yoon Suk Yeol, who warned last week that any use of nuclear weapons by Pyongyang would lead to "the end of the North Korean regime."

He condemned Yoon's "tasteless and vulgar comment" and said, "it shows he is totally consumed by his blind faith in his master's strength," KCNA quoted Kim as saying, referring to Seoul's alliance with the US.

Kim criticized South Korea and the US for destabilizing the region.

"To be honest, we have absolutely no intention of attacking South Korea," Kim said in his speech. He added that only his enemies' use of force would bring forth a response that would not exclude the use of nuclear weapons.

"Our footsteps toward becoming a military superpower and a nuclear power will accelerate," Kim added.

Last month, Pyongyang released images of a uranium enrichment facility, highlighting the North's aim to expand the country's nuclear weapons arsenal.

Tensions rise between North and South Korea

Meanwhile on Monday, the North Korean parliament was expected to declare a "two-state" system on the Korean Peninsula, formally rejecting reconciliation with Seoul.

The constitutional amendment would reflect Kim's stance that unification with South Korea is no longer a goal, declaring South Korea as a "principal enemy."

State media made no mention of the assembly's deliberations since Monday.

Current relations between the two Koreas are at a low point. Amid stalled diplomatic communication, the North has been engaging in provocative missile tests, while the South intensified its military exercises with the US.

Seoul also resumed anti-Pyongyang broadcasts in response to North Korea sending thousands of trash-filled balloons across the border.