SEOUL, South Korea — In his first speech in public since assuming the leadership of North Korea, Kim Jong-un said Sunday that his “first, second and third” priorities were to strengthen the military, and he declared that superiority in military technology was “no longer monopolized by imperialists.”

Mr. Kim’s speech was followed by what South Korean officials said was the North’s biggest display of weapons in a military parade, including a missile the North appeared to be presenting for the first time. While it is not clear whether it was a new long-range missile or a mock-up, its display demonstrates the importance that the North Korean government places on weapons development despite an embarrassing failure of a rocket it launched last week.

South Korean officials would not comment on the North Korean missile, pending further examination.

Mr. Kim’s claim to superior military technology could sound poignant, coming two days after the North Korean rocket carrying a satellite disintegrated in midair. The failure of the rocket indicated that North Korea might still have a long way to go before mastering the technology to deliver warheads atop an intercontinental ballistic missile.