North Korea has test-fired a missile into Japanese waters, the latest in a series of launches that have ratcheted up tensions over its nuclear weapons programme.

It was North Korea's third ballistic missile test in as many weeks and the 12th this year - carried out in fresh defiance of UN sanctions warnings and US threats of possible military action.

US military monitors said the short-range missile flew for six minutes, while Japan said it fell into the country's exclusive economic zone (EEZ) - waters extending 370km from its coast.

The launch comes despite tough talk from US President Donald Trump, who promised last week at the G7 summit that the "big problem" of North Korea "will be solved".

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Japan's Prime Minister Shinzo Abe swiftly condemned the test and vowed concerted action along with its US ally.

"We will never tolerate North Korea's continued provocations that ignore repeated warnings by the international community," Abe told reporters.

"As agreed during the G7 summit, the North Korean problem is the international community's top priority. In order to deter North Korea, we will take concrete action with the United States."

Monday's test, a short-range Scud, marks the second time this year that a North Korean missile fell provocatively close to its neighbour Japan.

It flew about 450 kilometres before landing in the Sea of Japan (East Sea) between the Korean peninsula and Japan, the US Pacific Command said.

Conflict 'catastrophic'

North Korea has been stepping up efforts towards its ultimate goal - developing an intercontinental ballistic missile that can deliver a nuclear warhead to the continental US.

The isolated but nuclear-armed North Korea has test-fired a missile almost every week for the past three weeks.

Michael Penn, president of the Tokyo-based Shingetsu news agency, said the latest test was part of a North Korean effort to strengthen its military against any possible threats from the US.

"The missile technology tests themselves do seem to be the priority of the North Korean regime, to get their technology as strong as possible, as quickly as possible, because they feel this is their best way forward - to show their own ability to defend themselves against a Trump administration they cannot predict," Penn told Al Jazeera.

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James Mattis, the US secretary of defence, in an interview that aired on Sunday before the launch, said the US favoured diplomacy over war with North Korea, which he said would be "catastrophic".

"The North Korean regime has hundreds of artillery cannons and rocket launchers within range of one of the most densely populated cities on Earth, which is the capital of South Korea," he told CBS News.

"This regime is a threat to the region, to Japan, to South Korea. And in the event of war, they would bring danger to China and to Russia as well.

"But the bottom line is, it would be a catastrophic war if this turns into a combat, if we're not able to resolve this situation through diplomatic means."

Mattis declined to say what kind of action from Pyongyang would constitute a "red line" for Washington, saying the administration needs "political manoeuvre room".

'Direct challenge'

South Korea's new president, Moon Jae-In, ordered a meeting of the national security council to assess the launch, which came a day after North Korea said its leader Kim Jong-un had overseen a test of a new anti-aircraft weapons system.

South Korea condemned the test as a "grave threat" and a challenge to the new leader who advocates dialogue with North Korea in a break from his conservative predecessors.

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"That the North repeated such provocations after the inauguration of our new leadership ... is a direct challenge to our demand for peace and denuclearisation of the Korean Peninsula," the foreign ministry said.

The missile launches, and Pyongyang's threat to stage its sixth nuclear test, have prompted calls for tougher UN sanctions and a warning from Trump that military intervention is an option under consideration.