North Korea fired a missile that flew over Japan’s northern Hokkaido far out into the Pacific Ocean on Friday, South Korean and Japanese officials said, further ratcheting up tensions after Pyongyang’s recent test of its most powerful nuclear bomb.

The missile flew over Japan and landed in the Pacific about 2,000 km (1,240 miles) east of Hokkaido, Japanese Chief Cabinet Secretary Yoshihide Suga told reporters.

Warning announcements about the missile blared around 7 am (2200 GMT Thursday) in the town of Kamaishi in northern Japan, footage from national broadcaster NHK showed.

US Secretary of Defense Jim Mattis said the launch “put millions of Japanese into duck and cover”, although residents in northern Japan appeared calm and went about their business as normal.

Observers say it is likely to have been an intermediate range ballistic missile (IRBM) though Japanese officials believe there is still a possibility it was an intercontinental ballistic missile (ICBM).

What is so alarming about the new launch is that the US Pacific territory of Guam, which North Korea says it has plans to fire missiles towards, is 3,400km from Pyongyang, putting it within range of the latest missile.

North Korea needs a nuclear-weapons programme to ensure its survival and there has been no let-up in its fiery rhetoric.

On Thursday, it threatened to "sink Japan and turn America to ashes".