North Korea informed Japan that it will launch a rocket between May 31 and June 11, identifying waters near the Yellow Sea, the East China Sea and to the east of Luzon Island in the Philippines as warning areas, a Japanese coast guard spokesman told AFP.

Such zones are usually designated for falling debris or rocket stages.

Japanese Prime Minister Fumio Kishida told officials to gather intelligence "on North Korea's notification about the launch of a ballistic missile that it describes as a satellite", his office said in a tweet.

"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, Kishida told reporters.

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

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 the North Korean military.

Because long-range rockets and space launchers share the same technology, analysts say developing the ability to put a satellite in orbit would provide Pyongyang with cover for testing banned intercontinental ballistic missiles (ICBMs).

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, but officials did not confirm to AFP if Seoul had been directly notified too.

"North Korea's so-called 'satellite launch' is a serious violation of UN Security Council resolutions banning all launches using ballistic missile technology, and is a clearly illegal act that cannot be justified under any pretext," the ministry said.

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

- Unusual stance -

Meanwhile, Kishida on Monday reiterated that Tokyo is open to talks with Pyongyang.

North Korean state media on Monday published a statement from the country's vice-minister of foreign affairs, appearing to endorse a conciliatory approach to relations with Japan -- an unusual stance from Pyongyang.

If Japan avoids "being shackled by the past, and seeks a way out for improving the relations, there is no reason for the DPRK and Japan not to meet", said the statement from Pak Sang Gil, using the initials of North Korea's official name.

Pak said, however, that Japan needs to move on from sticking points such as the "abduction issue" for ties to improve.

Japan suspects dozens of people who are still missing were abducted by North Korean agents in the 1970s and 1980s to train spies in the Japanese language and culture.