North Korea fired what the U.S. Pentagon said appeared to be an intercontinental ballistic missile (ICBM) that landed close to Japan on Wednesday, Pyongyang's first test launch since sending a missile over its neighbour in mid-September.

North Korea fired the missile a week after U.S. President Donald Trump put North Korea back on a U.S list of countries that Washington says support terrorism. The designation allows the United States to impose more sanctions, although some experts said it risked inflaming tensions on the Korean Peninsula.

Trump said of North Korea's latest test missile: "It is a situation that we will handle."

Trump said the launch did not change his administration's approach to North Korea, which has included new curbs to hurt trade between China and North Korea, which it sees as important to deterring Pyongyang from its ambition to develop a nuclear-tipped missile capable of hitting the United States.

Pentagon spokesman Col. Robert Manning said the Pentagon's initial assessment was that an ICBM was launched from Sain Ni in North Korea and travelled about 1,000 km before splashing down in the Sea of Japan. The missile did not pose a threat to the United States its territories or allies, the Pentagon said.

U.S. Defense Secretary Jim Mattis said the ICBM went higher than any shot Pyongyang has taken.

Japan's government estimated that the missile flew for about 50 minutes and landed in the sea in Japan's exclusive economic zone, Japanese broadcaster NHK said. A North Korean missile on Aug. 29 was airborne for 14 minutes over Japan.

Japanese Prime Minister Shinzo Abe said Tokyo was requesting an emergency meeting of the United Nations Security Council.

"We can never accept this violence and have strongly protested to North Korea," Abe told reporters. He called on all countries to strictly implement sanctions against Pyongyang.

South Korea's Joint Chiefs of Staff said Wednesday's missile was fired from Pyongsong, a city in South Pyongan Province, at around 1817 GMT over the sea between South Korea and Japan. The South Korean military said the missile had an altitude of around 4,500 km and flew 960 km.

Minutes after the North fired the missile, South Korea's military conducted a missile-firing test in response, the South Korean military said.

Japanese Defense Minister Itsunori Onodera said the missile reached an estimated altitude of 4,000 kilometres and broke up before landing in Japan's exclusive economic zone. He said it was judged to be ICBM class given the missile's lofted trajectory.

Japanese public broadcaster NHK reported three projectiles were fired, the nearest landing 210 kilometres west of Japan's northern mainland, suggesting the missile broke into pieces.

Japan's Kyodo news agency, quoting the defence ministry, said there were no reports of any damage.

U.S. stocks briefly pared gains on the news but the S&P 500 index was up almost one percent at the close.

A U.S. intelligence official said the initial indication was that the engine was not significantly more powerful than the Hwasong 14 which Pyongyang tested in July.

A 2,800-mile altitude, a 600-mile range, and a splash-down in the sea initially indicates that this was another test of the re-entry vehicle more than one of the missile, its engine, or its guidance system, said the official, who was studying incoming data on the launch.

Two U.S. government sources said earlier that U.S. government experts believed North Korea could conduct a new missile test within days.

After firing missiles at a rate of about two or three a month since April, North Korea paused its missile launches in September, after it fired a missile that passed over Japan’s northern Hokkaido island on Sept. 15.

The U.S. officials who spoke earlier declined to say what type of missile they thought North Korea might test.

Last week, North Korea denounced Trump's decision to relist it as a state sponsor of terrorism, calling it a "serious provocation and violent infringement."

Trump has traded insults and threats with North Korean leader Kim Jong Un and warned in his maiden speech to the United Nations in September that the United States would have no choice but to "totally destroy" North Korea if forced to defend itself or its allies.

Washington has said repeatedly that all options are on the table in dealing with North Korea, including military ones, but that it prefers a peaceful solution by Pyongyang agreeing to give up its nuclear and missile programs.

To this end, Trump has pursued a policy of encouraging countries around the world, including North Korea's main ally and neighbour, China, to step up sanctions on Pyongyang to persuade it to give up its weapons programs.

North Korea has given no indication it is willing to re-enter diplomatic talks on those terms.

North Korea has said its weapons programs is a necessary defence against U.S. plans to invade. The United States, which has 28,500 troops in South Korea as a legacy of the 1950-53 Korean war, denies any such intention.

Harry Kazianis, director of defence studies at Washington's conservative Center for the National Interest, said he thought North Korea might hold off on missile testing until about the time of the Winter Olympics, which South Korea is hosting next February, but added that North Korea had to keep testing to refine its weapons programme.

"I am surprised, but not shocked," he said. "North Korea tested two missiles in the fourth quarter last year and will have to continue to test its missile capabilities for years to come if it wants a nuclear deterrent that can hit the U.S."