By Soo-hyang Choi

SEOUL North Korean leader Kim Jong Un is believed to weigh over 140 kg (308 lb) according to an artificial intelligence (AI) estimate, a South Korean lawmaker said on Wednesday in a remark reflecting abiding interest in the health of the North's secretive ruler.

The health of North Korean leaders is typically a tightly held state secret, and speculation about the condition of the current leader Kim, believed to be 39 years old, has been recurring due to his heavy smoking, apparent weight gain and family history of cardiovascular problems.

"He appeared tired with clear dark circles around his eyes during his public appearance on May 16, and was estimated to weigh over 140 kilograms according to AI analysis," Yoo Sang-bum, a member of the parliamentary intelligence committee, told reporters after a briefing by the National Intelligence Service.

The lawmaker said Kim was believed to be suffering from a "severe" sleeping disorder, citing an intelligence report that North Korea has been intensively collecting latest medical information on insomnia treatment for its top official.

North Korea's tightly controlled state media rarely mentions the leader's health but in March, the North's Rodong Sinmun newspaper said Kim works until 5 a.m., quoting him as saying that he was used to working overnight, South Korea's Yonhap news agency reported.

Kim is a third-generation hereditary leader who came to power after his father Kim Jong Il died in 2011 from a heart attack.

South Korea's spy agency is monitoring the possibility of Kim falling into a "vicious cycle" of increased dependence on alcohol and nicotine, and experiencing worse insomnia given the large amount of foreign cigarettes and snacks being shipped into the North, Yoo said.

The briefing came hours after North Korea's sixth satellite launch ended in failure, with the booster and payload plunging into the sea.

Yoo said the North's Kim appears to have observed the launch on site.

(Reporting by Soo-hyang Choi, Editing by William Maclean)