North Korea's state-run media are heralding another visit by the country's young leader to a military installation – just days after a new book questioned Kim Jong Un's grip on power.

The North Korean Central News Agency said the young Kim inspected an army unit before posing for photos. It said during the inspection, the new supreme commander also waved enthusiastically to cheering soldiers while seeing how they trained and lived.

The visit is Kim's third with the military this year. Video released of his first visit – on New Year's Day – showed him shaking hands with soldiers and even sharing a laugh with military commanders.

The latest visit comes as a new book by a Japanese journalist with the Tokyo Shimbun newspaper paints a grim picture of North Korea's future.

The book quotes Kim Jong Un's older brother, Kim Jong Nam, as saying the regime is in danger of collapsing and that Kim Jong Un is nothing more than a figurehead.

Author Yoji Gomi says some of Kim Jong Nam's statements may reflect some jealousy but that he believes they are also insightful.

It is believed that Kim Jong Nam was groomed to succeed his father until he was caught trying to enter Japan on a false passport in 2001. Since then he has lived mostly in China.

Gomi says he met the elder son by chance at the airport in Beijing and has remained in contact with him. He says the book is based on several interviews in person and about 150 pieces of email.

The Associated Press quotes analysts as saying that Kim Jong Nam spends so much time outside his native land that his opinion carries little weight.

After the death of Kim Jong Il in December, North Korea's powerful military and its political leaders hastened to proclaim Kim Jong Un, the youngest of three sons, as his successor. The new leader is about 28 years old and observers say he has not had enough time to prepare for a leadership role.