"Unlike the other top officials in the North Korean regime, Kim Jong Un can not appear in public wearing a mask, because he can not be allowed to appear vulnerable to the North Korean people", said Balbina Hwang, a visiting professor at Georgetown University, said.
There were questions about his health after he missed the anniversary of the birth of Kim Il Sung on 15 April.
Mr. Kim, 36, had last appeared publicly on April 11.
The fertilizer plant has been the subject of attention for years because of its potential dual-use in the process of uranium extraction from phosphoric acid, allowing North Korea to hide its nuclear activities from the outside world. The North's official Korean Central News Agency hasn't reported about the incident. Other unconfirmed rumors suggested that North Korean doctors had sent the leader of the Workers' Party to Pyongyang, China for additional medical help, the paper notes.
Trump said Saturday he was pleased about Kim's reappearance and that the North Korean leader is apparently healthy.
Image Kim Jong Un was surrounded by officials during his visit to a fertiliser plant
The North is extremely secretive, and doubly so about its leadership.
In 2014, Kim disappeared for about 40 days, eventually reemerging with a cane.
Trump declined to comment yesterday on Kim resurfacing, telling reporters on the White House lawn, "I'd rather not comment on it yet, Kim Jong-Un". North Korea has become deadlocked in denuclearization talks with the US and now calls 2020 the year of a "full-frontal breakthrough" to counter United Nations sanctions by building its economy under its own efforts.
"This incident is a reminder of how vulnerable we remain to groundless rumours about North Korea", former United States government North Korea analyst Rachel Lee told AFP.
But the doubts won't fully be quelled without more evidence. But the efforts stalled amid a deadlock in nuclear negotiations between Kim and US President Donald Trump meant to convince North Korea to give up its arsenal.
© KCNA, via Associated Press Another image of Mr. Kim released by the state news agency, also said to have been taken Friday at the factory. Some Korea watchers, though, focused on state television footage of the event, which revealed a small, dark spot just above Kim's right wrist.
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