North Korea on Monday called US National Security Adviser John Bolton a "war monger" and "defective human product" after he called the North's recent tests of short-range missiles a violation of UN Security Council resolutions.

The statement by an unnamed North Korean foreign ministry spokesman came as President Donald Trump continued his visit to Japan for meetings with Japanese Prime Minister Shinzo Abe in which the nuclear standoff with North Korea was expected to be high on the agenda.

Bolton told reporters in Tokyo on Saturday that there was "no doubt" that North Korea's recent launches violated UN resolutions, and that sanctions against the North must be kept in place. Trump later downplayed the missile tests, tweeting, "North Korea fired off some small weapons, which disturbed some of my people, and others, but not me."

North Korea tested short-range ballistic missiles on May 4 and 9, ending a pause in launches that began in late 2017. The tests have been seen as a way for North Korea to pressure Washington to soften its stance on easing sanctions against it without actually causing negotiations to collapse.

Advertisement

In the statement carried by Pyongyang's official Korean Central News Agency, the North Korean spokesman said the North was rightfully exercising its rights of self-defense with the launches.

"Demanding us to ban all launches using ballistic technology regardless of range is same with asking us to relinquish our rights for self-defense," the spokesman said.

The spokesman said Bolton was an "ignorant" hard-liner who throughout different US administrations constantly pushed provocative policies against North Korea, which the spokesman said included endorsements of pre-emptive strikes and regime change.

The spokesman also said that Bolton's "hammer act" was responsible for the collapse of a major nuclear deal between the countries reached in 1994, when the North agreed to halt its nuclear programme in exchange for US fuel aid. The deal broke down in 2002 after US intelligence agencies said North Korea was continuing its pursuit of bombs with a secret uranium enrichment programme.

U.S. President Donald Trump, left, speaks as Japanese Prime Minister Shinzo Abe listens during a news conference at Akasaka Palace in Tokyo. Photo / AP
U.S. President Donald Trump, left, speaks as Japanese Prime Minister Shinzo Abe listens during a news conference at Akasaka Palace in Tokyo. Photo / AP

"Bolton should not be called a security adviser who works to secure security, but an adviser for security destruction who destroys peace and security," the spokesman said. "It's not that strange that crooked sound will always come out the mouth of a man who is structurally flawed, and it's best that this defective human product goes away as soon as possible."

Experts say the weapons North Korea tested this month are new solid-fuel missiles that are potentially nuclear capable and would strengthen the North's ability to conduct strikes on targets throughout South Korea.

But while expressing concern that the launches may run against the spirit of an inter-Korean military agreement reached last year to reduce tensions, South Korea has been eager to downplay the significance of the tests as it tries to keep a positive atmosphere for dialogue alive. South Korea's presidential office and military have refused to call the launches outright provocations, and have yet to confirm that the missiles were ballistic weapons, although most experts say they clearly were.

"There's no way for us to know why National Security Adviser Bolton made such comments," said a South Korean presidential official, who asked not to be named during a background briefing to reporters on Monday. "There's no change in our official stance that the South Korean and US militaries under coordination are continuing to analyse the missiles."

Advertisement

Negotiations between Washington and Pyongyang have been at a standstill since February, when a summit between North Korean leader Kim Jong Un and Trump broke down over what the United States described as the North's excessive demands for sanctions relief in exchange for a partial surrender of its nuclear capabilities. Kim since then has said the United States has until the end of the year to come up with mutually acceptable terms for a deal to salvage the negotiations.

Bolton acknowledged that the United States has not been "hearing much from North Korea" since the summit in Hanoi, Vietnam. The US special envoy to North Korea, Stephen Biegun, "can't wait to talk to his North Korean counterpart, but they haven't responded," Bolton said, adding that Biegun was "ready at any point to get on a plane and go anywhere."

The North Korean statement came as South Korea began its annual summertime defense drills involving thousands of civilians and troops. The drills have been modified to exclude large-scale military exercises with the United States that were suspended to create space for diplomacy with the North.

The four-day Ulchi Taeguk exercises will include massive civilian evacuation drills and a South Korea-only military drill aimed at preparing for war situations and disasters.

- AP