North Korea caused a new stir Wednesday by publicizing a purported mock-up of a key part of a nuclear warhead, with leader Kim Jong Un saying his country has developed miniaturized atomic bombs that can be placed on missiles.

The North's Rodong Sinmun newspaper carried photos on its front page showing Kim and nuclear scientists standing beside what outside analysts say appears to be a model warhead part -- a small, silverish globe with a ballistic missile or a model ballistic missile in the background.

The newspaper said Kim met his nuclear scientists for a briefing on the status of their work and declared he was greatly pleased that warheads had been standardized and miniaturized for use on ballistic missiles.

Information from secretive, authoritarian North Korea is often impossible to confirm and the country's state media have a history of photo manipulations. But it was the first time the North has publicly displayed its purported nuclear designs, though it remains unclear whether the country has functioning warheads of that size or is simply trying to develop one.

This also would be the first time Kim has been quoted directly about the miniaturized warheads. 

"The nuclear warheads have been standardized to be fit for ballistic missiles by miniaturizing them," state media agency KCNA quoted Kim as saying as he inspected a nuclear facility.

"This can be called true nuclear deterrent," he added.

The latest developments from the reclusive country come amid heightened tensions following claims it tested a hydrogen bomb in January.

On Monday at State of Air Force briefing at Pentagon, the Air Force's top officer Gen. Mark Welsh told Fox News, that while the actions of North Korea are "very worrisome," the country does not have the capability to put a nuclear warhead on top of a missile and shoot it at the United States.

North Korea warned Monday of pre-emptive nuclear strikes after the United States and South Korea began holding their biggest ever war games.

Tensions remain high after North Korea's recent nuclear test and rocket launch, which prompted the United Nations to adopt tough new sanctions.

Fox News' Lucas Tomlinson and The Associated Press contributed to this report.