The North Korean leader Kim Jong-un delivers his first public speech at a major military parade in Pyongyang. Image Credit: AFP

Pyongyang: North Korea's new leader delivered his first major public speech yesterday as the impoverished state celebrated the centenary of its founder's birth, calling for a push to "final victory" despite a failed rocket launch two days earlier.

Kim Jong-un, clad in black and the third of his line to rule North Korea, read monotonously from a script in Pyongyang's central square after goose-stepping soldiers and sailors showcased the North's military power in a parade in spring sunshine.

Smiling and joking with generals on a podium after the speech, Kim watched as the country's missiles paraded past, a reminder that despite Friday's embarrassing failure to successfully launch a rocket, North Korea packs a punch.

In a move that indicated Kim would stick to the "military-first" policies that have put North Korea on the verge of nuclear-weapons capacity, he lauded respectively his grandfather, Kim Il-sung, and his father, Kim Jong-il, as the "founder and the builder of our revolutionary armed forces".

North Korea is believed to be readying a third nuclear test, based on intelligence satellite images and a past pattern of rocket launches followed by tests. "Let us move forward to final victory," the 20-something leader urged tens of thousands of military and civilians as they applauded his more than 20-minute speech, the first time a North Korean leader has delivered a major public set-piece address.

Thousands of goose-stepping soldiers held up coloured cards to spell out Kim Jong-un's name and the words "strong and prosperous".

The crowd waved artificial pink flowers, celebrating the two dead Kims who ruled the nation in an event that was hosted by one of the country's top generals, Ri Yong-ho.

South Korea's Yonhap news agency and YTN TV later cited military sources and analysts as saying the North unveiled at the parade a new long-range missile, presumed to be a ballistic missile with a range of up to 6,000km.

The missile appeared to be longer and with a bigger diameter compared with others, the North has revealed.

"In order to enhance the dignity of Songun [military-first] Chosun [Korea] and to accomplish the task of building a strong and prosperous socialist country, we have to make every effort to reinforce the people's armed forces," Kim said.

Given Kim Jong-il's years of silence, North Korea specialists said the speech was likely another attempt to remind people of happier days under Kim Il-sung, a revered and avuncular figure the new ruler closely resembles.

"It shows a new governing style for the Kim Jong-un era," said Koh Yu-hwan, a professor at Dongguk University's department of North Korea studies.

North Korea departed from its usual practice of not telling its population about embarrassing failures when state television on Friday broadcast news that a rocket had failed to put a satellite into orbit.

Critics say the long-range rocket launch was part of a bid to develop a ballistic missile capable of delivering a nuclear warhead to hit the US.