SEOUL, South Korea - One photo shows a chubby-cheeked boy with an impish grin. Former classmates at a Swiss boarding school describe a shy student who loved basketball and Jean-Claude Van Damme. Recent reports describe him as overweight and a heavy drinker.

Now 26, Kim Jong Un has reportedly been tapped to become the next leader of nuclear-armed North Korea.

The youngest son of authoritarian leader Kim Jong Il, he appears to have led a cloistered life, pulled back home after his Swiss schooldays and kept out of the limelight.

But he is already being hailed as "our Commander Kim," and North Koreans are busy learning the lyrics to a new song praising him as the next leader of the world's first communist dynasty, South Korea's Dong-a Ilbo newspaper said yesterday.

South Korea's spy agency told lawmakers the Pyongyang regime has begun "pledging its allegiance to Kim Jong Un," legislator Park Jie-won said yesterday. The Hankook Ilbo newspaper said the announcement was made after North Korea's provocative underground nuclear test last week.

The National Intelligence Service refused to confirm the reports.

For years, Kim Jong Il's eldest son, Jong Nam, 38, was considered the favorite to succeed his father until he was caught trying to enter Japan on a fake passport in 2001, reportedly to visit the Disney resort.

Kim considers the middle son, Jong Chol, too effeminate, according to the leader's former sushi chef.

Jong Un, however, is the "spitting-image" of his father and the leader's favorite, the chef, who goes by the pen name Kenji Fujimoto, wrote in a 2003 memoir.

Jong Un reportedly is the only one of the sons with a military background, key in a regime run on a "songun," or "military first," policy, said Paik Hak-soon of the Sejong Institute, a think tank located outside Seoul.

Jong Un's uncle Jang Song Thaek, a member of the all-powerful National Defense Commission with strong military and political connections, will likely guide and advise him, he said, noting that Jang is in charge of North Korean intelligence, and has political control of the prosecutor's office, the police and the courts.

The apparent anointment comes at a time of mounting tensions over the May 25 nuclear test and North Korea's April 5 rocket launch. The North also appears to be preparing to test-fire an array of medium- and long-range missiles, reports said. Global powers are discussing how to rein in Pyongyang for its nuclear defiance.

Analysts say the saber-rattling is part of a campaign to build unity and support for a successor to the 67-year-old Kim Jong Il, who reportedly suffered a stroke last August and looked gaunt and markedly grayer in an April appearance at parliament.

Kim is believed to want to name a successor by 2012 - the centenary of the birth of his father, North Korea's founder, Kim Il Sung - and the regime undertook a massive campaign last year to gear up for the celebrations.

The regime stepped up the pace last month, launching a "150-day battle" urging North Koreans to work harder to build the country's economy.

"Before 2012, North Korea must convince the army and the public that Jong Un is the best successor," said Atsuhito Isozaki, assistant professor of North Korean politics at Tokyo's private Keio University. "To pave the way for Jong Un's leadership, it is highly likely that North Korea will turn recent nuclear and missile tests into his achievements."

Little is known about Kim Jong Un. Unlike his eldest brother, who is closely trailed by the media during gambling trips to Macau, Jong Un has made few public forays overseas since his Switzerland days.

The one photo purportedly showing him as a boy cannot be verified, and there are no known images of Jong Un as an adult.

A Swiss news magazine, L'Hebdo, reported earlier this year that classmates recalled him as timid and introverted, but an avid skier, basketball player and fan of NBA star Michael Jordan.

After returning to Pyongyang, he attended the Kim Il Sung Military University, graduating in 2007, Yonhap said. Unnamed sources described him as ambitious and "aggressive, shrewd and capricious."

But there are rumors the 2004 death of his mother, Japanese-born former dancer Ko Yong Hi, took a toll on the young man, Yonhap said.

A diminutive 5-foot-6, he drank heavily after her death from cancer and ballooned to nearly 200 pounds, and is now suffering from high blood pressure and diabetes, the report said. *