Pyongyang, North Korea - North Korea fired several short-range ballistic missiles into the sea Tuesday, according to Seoul's military, in what experts said could be a message to US President-elect Donald Trump's incoming administration.

The launch comes as Japanese Foreign Minister Takeshi Iwaya visits South Korea for a series of meetings with top officials, with the Asian neighbors seeking to boost bilateral ties before Trump returns to office next week.

"The South Korean military detected several short-range ballistic missiles fired into the East Sea," Seoul's military said, referring to the body of water also known as the Sea of Japan.

It said the launch took place around 9:30 AM local time near North Korea's Ganggye area, with the missiles flying 155 miles before landing in the sea.

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The Tuesday launch is Pyongyang's second this year, after it fired last week what it said was a new hypersonic missile system.

The location of the test site was undisclosed, but images released by North Korean state media KCNA showed leader Kim Jong Un observing last week's launch with his teenage daughter Ju Ae.

"The intelligence authorities of South Korea and the US have detected and monitored North Korea's missile launch preparations in advance, and immediately detected and tracked them at the time of launch," South Korea's military said Tuesday.

It added that it was maintaining "full readiness" and sharing information with the US and Japan, while "strengthening surveillance and alertness" for more launches.

Seoul's acting president Choi Sang-mok slammed the launch, saying it violated UN Security Council resolutions.

"Seoul will respond more strongly to North Korea's provocations based on its strong security posture and alliance with the US," he said.

Experts said Pyongyang's latest move could be intended as a message to the incoming Trump administration.

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"It could be aimed at the US," said Yang Moo-jin, president of the University of North Korean Studies in Seoul.

"It may indicate an intention to put pressure ahead of the Trump administration's second term."

Ahn Chan-il, a defector-turned-researcher who runs the World Institute for North Korea Studies, told AFP the test launch "appears to be an intention to assert presence ahead of the Trump administration".

He said it could also be aimed at "destabilizing South Korea during Seoul's own period of turmoil", as suspended President Yoon Suk Yeol faces an impeachment trial that begins Tuesday in the Constitutional Court after a failed martial law bid last month.