North Korean missile prompts emergency alert by Japan — and confusion

North Korea fired a ballistic missile of intermediate range or longer on Thursday, South Korea and Japan said, prompting an alert for residents of Japan's northern island of Hokkaido to take cover.

After first saying the country's J-Alert emergency warning system had made an erroneous prediction that the missile would fall near the island and retracting it, the Japanese government later said the emergency evacuation warning was appropriate and not an error.

"We did not correct the information issued by the J-Alert [system]," Chief Cabinet Secretary Hirokazu Matsuno told a news conference.

The missile flew about 1,000 kilometres, South Korea's military said, calling it a "grave provocation." Its apogee, or maximum altitude, has not been disclosed.

Japanese Prime Minister Fumio Kishida said his government would hold a National Security Council meeting on the launch.

A TV screen in Tokyo displays a warning message after the missile launch. (Issei Kato/Reuters)

Defence Minister Yasukazu Hamada said earlier the missile appeared to have been fired eastward at a high angle and did not fall in Japanese territory. He said the ministry was analyzing the launch for more details.

Hamada said he could not confirm whether the missile flew over Japan's exclusive economic zone.

Japan's coast guard said a projectile that appeared to be the missile had fallen into the sea east of North Korea.

There have been problems with J-Alert before.

In October, an evacuation warning was issued when a missile overflew Japan but came so late most people were not aware of it until the projectile had fallen into the Pacific.

A month later, a warning was erroneously issued saying a missile had overflown Japan.

On Thursday, a student told Japanese broadcaster NHK that the alert caused momentary alarm at a train station in Hokkaido.

"For a second in the train there was panic, but a station worker said to calm down, and people did," said the man, whom NHK did not name.

The launch came days after North Korean leader Kim Jong-un called for a strengthening of the country's war deterrence in a "more practical and offensive" manner to counter what the country called moves of aggression by the United States.

The U.S. said late Wednesday it "strongly condemns" North Korea for the launch.

"The door has not closed on diplomacy, but Pyongyang must immediately cease its destabilizing actions and instead choose diplomatic engagement," National Security Council spokesperson Adrienne Watson said in a statement.

The missile was fired at 7:23 a.m. local time from near Pyongyang, South Korea's Joint Chiefs of Staff said. The J-Alert system sent out a warning about 30 minutes later. It was cancelled just after 8 a.m. local time.

The South Korean military said it was on high alert and maintaining readiness in close co-ordination with the U.S.

North Korea has criticized a recent series of joint military exercises between the U.S. and South Korea as escalating tensions, and has stepped up its weapons tests in recent months.