NORTH Korean leader Kim Jong Un spoke publicly for the first time yesterday, praising his father Kim Jong Il's "military first" policy during celebrations marking the 100th birthday of the nation's late founder.

Kim, who has been seen but not publicly heard since taking over after Kim Jong Il's death in December, stepped to the podium to speak before tens of thousands of people gathered in Pyongyang's main square for meticulously-choreographed festivities to glorify his grandfather, North Korea's founder, Kim Il Sung.

Kim Jong Un said the era when nuclear arms could threaten his country was "forever over".

He called for strengthening the country's "military first" policy by making military might the "first, second and third" priorities.

He said his country had built a "mighty military" capable of both offence and defence in any type of modern warfare.

"Superiority in military technology is no longer monopolised by imperialists," he said.

North Korea defied the US and others on Friday by firing a long-range rocket that space experts said carried an observational satellite, despite warnings against pushing ahead with the provocative launch. Washington and others say it was a covert test of long-range missile technology.

Hours after the rocket broke up over the Yellow Sea, the country made an unusual admission of failure, but Kim did not mention the launch yesterday.

The United Nations Security Council condemned the launch as a violation of resolutions that ban North Korea from developing nuclear and missile programmes.