A Korean mystery: Where’s the North’s leader?

South Korean officials are questioning the accuracy of a report by Daily NK, a website based in Seoul that relies on sources in North Korea, that Kim Jong-un, 36, is recovering from heart surgery performed on April 12.

Mr. Kim last appeared in public on April 11, when he presided over a meeting of the Politburo of the ruling Workers’ Party. It is not unusual for senior North Korean leaders to stay out of view for weeks at a time, but when Mr. Kim didn’t appear on April 15 to commemorate the birthday of his grandfather, Kim Il-sung, the founder of the regime, it triggered speculation about his health and whereabouts.

Context: The inner workings of the top leadership in Pyongyang have been cloaked in such secrecy that disappearances like these always catch the attention of analysts. When Mr. Kim’s father, Kim Jong-il, died in 2011, foreign intelligence officials didn’t know until the news was announced two days later on North Korean television.