The latest launches come as US, Japan and South Korea wrap up three days of military exercises dubbed ‘Freedom Edge’.

Monday’s launches came a day after Pyongyang promised “offensive and overwhelming” responses to new military drills staged by the United States, South Korea and Japan.

South Korea’s Joint Chiefs of Staff said in a statement that the missiles were launched 10 minutes apart in a northeasterly direction from the town of Jangyon in southeastern North Korea.

The military said the first missile flew 600km (370 miles) and the second for 120km (75 miles), but did not say where they landed. North Korea typically test-fires missiles towards its eastern waters, but the second missile’s flight distance was too short to reach that far.

Joint Chiefs of Staff spokesperson Lee Sung-joon later told a briefing there appeared to have been problems with the second missile and that if it exploded, its debris would probably have scattered on the ground.

South Korean media, citing unidentified South Korean military sources, said it was highly likely the second missile crashed in an inland area of North Korea, while the first one landed in the waters off the country’s eastern city of Chongjin.

Monday’s launches were the first from North Korea in five days and came as the US, South Korea and Japan ended their “Freedom Edge” drills, new multi-domain trilateral military exercises.

Pyongyang typically frames such drills as rehearsals for an invasion or proof of the countries’ hostility.

“In both North Korean politics and military policy, the best defense is often a good offense,” Leif-Eric Easley, professor of international studies at the Ewha Womans University in Seoul, said in emailed comments. “Pyongyang is also determined not to appear weak while South Korea conducts defense exercises with Japan and the United States.”

Last Wednesday, North Korea launched what it called a multiwarhead missile in the first known test of a developmental, advanced weapon meant to defeat US and South Korean missile defences, although South Korea disputed the claim. It said Pyongyang had launched what appeared to be a hypersonic missile but it spiralled out of control and exploded.

On Friday, North Korea began a key ruling party meeting to determine what it called “important, immediate issues” related to works to further enhance Korean-style socialism. Observers said the meeting was continuing on Monday.