Earlier in the day, the JCS said the two missiles were launched just after dawn from Wonsan on the North's east coast and flew more than 430 kilometres (270 miles) before falling into the sea.

But it released a separate statement later, saying the second weapon fired by the North flew 690 kilometres and was understood to be a "new type of missile", citing an analysis by South Korean and US intelligence authorities.

It was the North's first missile test since an impromptu meeting between US President Donald Trump and North Korean leader Kim Jong Un last month that produced an agreement to resume a working-level denuclearisation dialogue.

Analysts said the latest tests signalled Pyongyang's anger over planned US-South Korea joint military exercises scheduled for next month.

Pyongyang earlier launched short-range missiles in May, which Trump dismissed at the time as "very standard stuff" that would have no impact on his relationship with Kim.

The two leaders went on to hold an unscheduled meeting June 30 in the Demilitarized Zone that divides the two Koreas, where they agreed to pick up a nuclear dialogue that stalled after the collapse of a formal summit in Hanoi in February.

US Secretary of State Mike Pompeo said the working-level disarmament talks would probably start in mid-July, but last week Pyongyang said they had been jeopardised by the scheduled joint military drills.