The US government has extensive contingency plans in place in case North Korean leader Kim Jong-un dies or is unable to rule due to failing health, Fox News reported Wednesday, adding that the plans involve China to address the potential for a mass-scale humanitarian crisis.

Any mass exodus of North Korean refugees would need China’s support, according to unnamed sources in the US government the new channel cited.

The report came amid lingering speculation concerning Kim’s well-being, with some floating the possibility he might be incapacitated after undergoing heart surgery.

A day earlier on Tuesday, CNN reported that Kim was gravely ill, jolting financial markets in Seoul. South Korea’s presidential office brushed off the report, saying there were no unusual signs coming from Pyongyang.

On Monday, Daily NK, a Seoul-based online media outlet, said Kim appeared to be receiving treatment after undergoing a cardiovascular procedure on April 12. But South Korea’s Unification Ministry reaffirmed its stance Wednesday, saying there still were no unusual signs to back such claims.

“We’ve seen letters exchanged between leaders for congratulatory and birthday events,” a ministry official said, referring to the North’s media reports that Kim had sent congratulatory messages to several countries, including one to Syria on Saturday, another to Zimbabwe on Sunday and to Cuba on Tuesday.

The state media said Wednesday Kim had replied to a letter from the Syrian president congratulating him on the anniversary of his grandfather’s birth on April 15.

John Hyten, vice chairman of the US Joint Chiefs of Staff, assessed likewise, saying Kim was still in full control of North Korea’s armed forces, including its nuclear arsenal.

Hyten told a press briefing Wednesday he had no reason to think otherwise, but added that he did not have enough intelligence to confirm or deny the reports.

US President Donald Trump said his administration did not know whether Kim was ill, while his national security adviser Robert O’Brien said the US was closely monitoring reports on Kim and keeping an eye on North Korea.

Kim’s absence from the anniversary event on April 15, a national holiday he had observed every year since coming to power in 2012, prompted the global speculation, which North Korea has yet to publicly address.

Seoul officials said Pyongyang has never officially responded to rumors concerning high-profile figures, and that its state-run media may soon reveal what the 36-year-old leader has been up to recently.

By Choi Si-young (siyoungchoi@heraldcorp.com)