North Korea's launch of four missiles were a training exercise for a strike on US bases in Japan, the country's state media says.

North Korea has warned that US-South Korean military exercises are driving the Korean Peninsula and northeast Asia toward "nuclear disaster".

The reclusive state fired four ballistic missiles into the sea off Japan's northwest on Monday (NZT), angering South Korea and Japan.

Kim Jong Un supervised the test launches which were by an army unit commissioned with attacking US military bases in Japan, the country's state media said on Tuesday (NZT).

KCNA North Korean leader Kim Jong Un supervised the test launches which were by an army unit commissioned with attacking US military bases in Japan.

The launches were a training exercise for a strike on those bases, it said.

The North Korean ambassador to the United Nations, Ja Song Nam, said in a letter to the UN Security Council hours after the missiles were launched that the US-South Korea exercises were the "the most undisguised nuclear war manoeuvres".

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REUTERS North Korea's ambassador to the United Nations, Ja Song Nam said the region was inching to the brink of nuclear war.

Nam said the US was using nuclear-propelled aircraft carriers, nuclear submarines, nuclear strategic bombers and stealth fighters in the joint exercises that began on Thursday (NZT).

"It may go over to an actual war," Ja warned of the military drills, "and, consequently, the situation on the Korean Peninsula is again inching to the brink of a nuclear war".

URGENT SECURITY COUNCIL MEETING

The United States and Japan, in consultation with South Korea, have requested an urgent Security Council meeting on the North Korean launches.

The closed consultations are likely to take place on Thursday (NZT) after the Security Council returns from a visit to four Boko Haram-affected countries in Africa, a UN diplomat said, speaking on condition of anonymity because consultations have been private.

Ri Song Chol, a counsellor at North Korea's UN mission, said the missile launches were a continuation of Supreme Leader Kim Jong Un's efforts "to strengthen our self-defensive military forces and pre-emptive attack capabilities" in response to "nuclear threats and blackmails" and the US-South Korean military exercises.

He accused the United States of spurring the North to develop an intercontinental ballistic missile and reiterated a Foreign Ministry statement issued in January 8 that an ICBM would be launched "in any time and in any place decided by our supreme leadership."

Ri claimed the current joint military exercises are "for pre-emptive strike to the DPRK" - the initials of the country's official name, the Democratic People's Republic of Korea.

He said that is in contrast to previous annual exercises that the US and South Korea called preventive and defensive.

UN A 'POLITICAL TOOL' OF THE US

Ja, the ambassador, again urged the Security Council to discuss the US-South Korea exercises and warned that if it ignores North Korea's request, as it has in the past, it will demonstrate the UN's most powerful body is only a "political tool" of the United States.

He said the United States seeks to convince public opinion that the latest joint exercise is a response to North Korea's nuclear weapons, but he said the US and South Korea carried out military drills numerous times before Pyongyang possessed its "nuclear deterrent".

Ja said the main reason North Korea is equipping itself "with nuclear attack capabilities" and strengthening its nuclear deterrent forces is in self-defense against what he called the US "extreme anti-DPRK hostile policy and nuclear threats and blackmails as well as manoeuvres to enforce its nuclear weapons".

US BEARS 'FULL RESPONSIBILITY' FOR KOREA INSTABILITY

North Korea's UN mission also issued a statement denouncing and rejecting a report by the Security Council's panel of experts that monitors UN sanctions against the North.

The experts said North Korea is flouting sanctions by trading in prohibited weapons and other goods and using evasion techniques "that are increasing in scale, scope and sophistication".

The North Korean mission again insisted that UN sanctions "have no legal basis at all" and violate the country's "lawful rights".

Furthermore, it contended no international law states that a nuclear test or satellite launch should be considered a "threat to international peace and security".

The mission reiterated its request to UN Secretary-General Antonio Guterres to organise an international forum of lawyers to clarify the legal basis of the sanctions resolutions.

It said the UN Secretariat should not again respond with the "preposterous out-of-date sophistries" that it is up to the Security Council to determine what constitutes a threat to international peace and security.

The North also warned that sanctions resolutions and reports on enforcing implementation will only result in "our stronger self-defensive counter-measures" - and it said the United States, will bear all responsibility "for any uncontrolled critical situation over the Korean Peninsula".

- AP AND AAP