A rocket carrying the satellite blasted off Tuesday night from North Phyongan province and "accurately put the reconnaissance satellite 'Malligyong-1' on its orbit", state-run news agency KCNA reported.

Images in state media showed North Korean leader Kim Jong Un smiling and waving, surrounded by white-uniformed scientists and engineers who cheered and clapped after watching the successful blastoff.

The United States led condemnation of the launch, saying it was a "brazen violation" of UN sanctions, while South Korea responded by partially suspending a 2018 military deal with the North, saying it would resume surveillance operations along their border.

Japan said that Pyongyang's claims of success could not immediately be independently verified.

Tokyo is still analysing the launch and "at this point is not confirming whether the satellite had entered into an orbit around the Earth", chief government spokesman Hirokazu Matsuno said.

North Korea's previous efforts to put a spy satellite into orbit in May and August both failed. Seoul, Tokyo and Washington had repeatedly warned Pyongyang not to proceed with another launch, which would violate successive rounds of UN resolutions.

Space launch rockets and ballistic missiles have significant technological overlap, experts say, and Pyongyang is barred by UN resolutions from any tests involving ballistic technology.

Seoul's spy agency this month said Pyongyang appeared to have received technical advice from Russia in return for sending at least 10 shipments of weapons for Moscow's war in Ukraine.

KCNA said it was North Korea's "legitimate right" to launch the satellite, as the country confronts what it calls threats from South Korea and the United States.

The North plans to launch more satellites "in a short span of time" to step up its surveillance capability on South Korea, KCNA said.

A South Korean defence official said after the launch that Seoul would "restore aerial surveillance and reconnaissance activities for signs of North Korean provocations" along the border, calling them "equivalent and minimal defensive measures against North Korea's provocation".

"If North Korea carries out additional provocations, our military will immediately and strongly punish any provocations," he told a briefing.

- 'Confidence in success' -

Seoul has been saying for weeks that Pyongyang was in the final stages of preparation for another attempted spy satellite launch.

The North's May attempt failed due to the "abnormal" startup of its second-stage engine, Pyongyang state media said at the time, while the August misfire was attributed to an error in the "emergency blasting system".

Wednesday's launch comes after Russian President Vladimir Putin suggested in September after meeting with North Korean leader Kim Jong Un that his nation could help Pyongyang build satellites.

Seoul and Washington have both subsequently accused Pyongyang of shipping weapons to Russia, with US Secretary of State Antony Blinken warning this month that military ties between North Korea and Russia were "growing and dangerous".

The launch also appears to kick off a space race on the peninsula, experts said, with Seoul planning to launch its first spy satellite via a SpaceX rocket later this month.

"Kim Jong Un demonstrated his will to have an upper hand in military superiority by attempting to launch the first military reconnaissance satellite into orbit before South Korea," said Lim Eul-chul, associate professor at the Institute for Far Eastern Studies, Kyungnam University.

"Of course, it appears that there will be differences in the performance of the satellites."

Successfully putting a spy satellite into orbit would improve North Korea's intelligence-gathering capabilities, particularly over South Korea, and provide crucial data in any military conflict, experts say.

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