North Korea has said it would launch a spy satellite in June, claiming it was necessary to monitor the "dangerous" military movements of the United States and its allies.

Criticising US-South Korea joint military exercises, including the ongoing large-scale live-fire drills, a top North Korean military official confirmed Tuesday that "military reconnaissance satellite No. 1" would be launched next month.

The statement came a day after North Korea notified Japan's coast guard that the launch, sometime between May 31 and June 11, might affect waters in the Yellow Sea, East China Sea and east of the Philippines' Luzon Island.

Tokyo warned the launch would likely violate United Nations sanctions. Satellite launch technology overlaps significantly with that used in ballistic missiles, which Pyongyang is explicitly prohibited from using under UN sanctions.

The official Korean Central News Agency cited Ri Pyong Chol, vice-chairman of the ruling party's central military commission, saying the satellite was "indispensable to tracking, monitoring ... and coping with in advance in real time the dangerous military acts of the US and its vassal forces."

Citing "reckless" acts by Washington and Seoul, Ri said North Korea felt "the need to expand reconnaissance and information means and improve various defensive and offensive weapons".

The official also accused the United States of conducting "hostile air espionage activities on the Korean peninsula and in its vicinity," according to the KCNA dispatch.

Pyongyang, which typically does not give advanced warning of missile launches, has been known to inform international bodies of purportedly peaceful satellite launch plans.

"Even if it's described as a satellite, a launch using ballistic missile technology would be a violation of United Nations Security Council resolutions" and would threaten people's safety, Japanese Prime Minister Fumio Kishida said.

In 2012 and 2016, Pyongyang tested ballistic missiles that it called satellite launches. Both flew over Japan's southern Okinawa region.

Blaming US, South Korea

"North Korea is giving justification and legitimacy to the upcoming launch of a military reconnaissance satellite, by blaming the ongoing US-South Korea joint drills," Yang Moo-jin, president of the University of North Korean Studies in Seoul, told AFP news agency.

He said that although satellites and ballistic missiles differ in their missions, the technology was effectively identical.

"If North Korea launches a satellite, it will be a violation of UN security resolutions, as it bans all launches using ballistic missile technology."

North Korean leader Kim Jong Un this month inspected the country's first military spy satellite as it was prepared for launch, and gave the green light for its "future action plan."

In 2021, Kim had identified the development of such satellites as a key defence project for t he North Korean military.

Japan's defence ministry issued an order to shoot down any ballistic missile confirmed to be on course to fall into its territory.

South Korea's foreign ministry condemned the launch plan, saying the "so-called 'satellite launch' is a serious violation of UN Security Council resolutions banning all launches using ballistic missile technology."

South Korea and Japan have been working to mend long-frayed ties, including through greater cooperation on North Korea's military threats.