North Korea has notified Japan it plans to launch a satellite in what Tokyo and Seoul said could be a third attempt to put a spy satellite into orbit in violation of a UN ban.
Japan's Coast Guard said on Tuesday the North gave notice of the launch between Wednesday and December 1 in the direction of the Yellow Sea and East China Sea.
South Korea's state maritime safety agency issued a warning to vessels of the planned launch for the same areas as previous launches.
North Korea had attempted to launch what it called spy satellites twice earlier this year but failed, and South Korean officials have said in recent days that it appeared set to try again soon.
State media KCNA reported on Tuesday it was North Korea's "sovereign right" to strengthen its military power against the US-led space surveillance system and defended its military satellite development, citing a researcher at the nuclear-armed state's space agency.
The notice prompted immediate condemnation from Japanese Prime Minister Fumio Kishida, who said his country's defence systems, including the Aegis destroyers and PAC-3 air defence missiles, stood ready for any "unexpected situation" that arose.
"Even if the purpose is to launch a satellite, using ballistic missile technology is a violation of a series of United Nations Security Council resolutions," Kishida told reporters.
"It is also a matter that greatly affects national security."
Japan will work with the United States, South Korea and others to "strongly urge" North Korea not to go ahead with the launch, Kishida said.
South Korea's defence ministry said it was watching the North's planned launch.
Previous launches came in the early hours of the first day of the window, the ministry said, and it was possible the third attempt would be successful.
North Korea has notified Japan, as the co-ordinating authority for the International Maritime Organisation for those waters, of its satellite launch plans previously.
Pyongyang considers its space and military rocket programmes a sovereign right, and has said it plans a fleet of satellites to monitor moves by US and South Korean troops.
It has made multiple attempts to launch what it called "observation" satellites, two of which appeared to have successfully reached orbit.
Analysts say spy satellites are crucial to improving the effectiveness of North Korea's weapons.
The launch would be the first since North Korean leader Kim Jong-un toured Russia's modern space station in September where President Vladimir Putin promised to help Pyongyang build satellites.
North Korea's notice follows its denouncement on Monday of the potential US sale of hundreds of missiles to Japan and South Korea, calling it a dangerous act and vowing to boost deterrence and respond to increased tension.
On Monday, South Korea's military issued a warning demanding North Korea call off any plan to launch a satellite, describing it as an act of provocation that threatens South Korea's security.
South Korea separately plans to launch its first reconnaissance satellite from California on November 30 with the aid of the United States.
Australian Associated Press