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North Korea on Friday test-fired its second intercontinental ballistic missile, which flew longer and higher than the first according to its wary neighbours, leading analysts to conclude that a wide swath of the U.S., including Los Angeles and Chicago, is now within range of Pyongyang's weapons.

Japanese government spokesman Yoshihide Suga said the missile, launched late Friday night, flew for about 45 minutes — about five minutes longer than the ICBM North Korea test-fired on July 4. The missile was launched on very high trajectory, which limited the distance it travelled, and landed west of Japan's island of Hokkaido.

"We assess that this missile was an intercontinental ballistic missile, as had been expected," Pentagon spokesman Navy Capt. Jeff Davis said in Washington.

Analysts had estimated that the North's first ICBM could have reached Alaska, and said Friday that the latest missile appeared to extend that range significantly.

David Wright, a physicist and co-director of the global security program at the Union of Concerned Scientists, said in Washington that if reports of the missile's maximum altitude and flight time are correct, it would have a theoretical range of at least 10,400 kilometres (about 6,500 miles). That means it could have reached Los Angeles, Denver and Chicago, depending on variables such as the size and weight of the warhead that would be carried atop such a missile in an actual attack.