SEOUL • What was the silver spherical object seen in newly released pictures of North Korean leader Kim Jong Un with his country's top nuclear scientists?

Is it part of a miniaturised thermonuclear warhead that Mr Kim claimed this week his country has developed? Is it even real?

Experts on North Korea's missile programme are divided on these questions following the publication of the front-page picture in Rodong Sinmun, the North Korean ruling party's newspaper. The caption did not explicitly say what the device was.

According to Mr Karl Dewey, senior analyst for IHS Jane's, it is unlikely that the silver spherical device is a thermonuclear, or hydrogen, bomb.

"Thermonuclear weapons are multi-stage devices, and in modern weapons, the need to place two separate stages together would result in a more oblong-like structure," he wrote on Wednesday.

Nuclear expert Whang Joo Ho of Kyung Hee University told Associated Press that the object was obviously a prototype because Mr Kim and others would not stand near an actual device because of concerns about radioactivity.

In the background of the photo, published on Wednesday, was a camouflage missile. It is believed to be North Korea's KN-08 inter-continental ballistic missile (ICBM), which could reach the western coast of the United States.

Even if Pyongyang has managed to develop a bomb small enough to fit into a warhead, experts say the country still has a lot of work ahead to be able to deliver it effectively. North Korea has, to date, never tested its KN-08 ICBM, according to The Diplomat magazine.