South Korea's Unification Minister Kim Yeon-chul on Tuesday rejected unconfirmed reports of North Korean leader Kim Jong-un's health as "fake news" and "infodemic", insisting he can say confidently there have been no unusual signs in Pyongyang.

Speculation about Kim's health spiked after he skipped an annual visit to the mausoleum of his grandfather Kim Il-sung on the late national founder's April 15 birth anniversary, the North's most important national holiday, reports Yonhap News Agency.

Media reports have since speculated that Kim Jong-un might be seriously ill, but South Korean officials have disputed the reports, repeatedly saying there were no unusual signs found in North Korea and that the leader was believed to be staying in the country's eastern coastal town of Wonsan.

"It can be seen as a phenomenon of infodemic," the Unification Minister said during a parliamentary foreign affairs committee meeting, referring to a recent deluge of unfounded rumours about the leader's heath.

"We have intelligence capacity that allows us to say confidently that there are no unusual signs."

In a report last week, CNN said that the US was looking into intelligence that Kim Jong-un was in "grave danger" after a surgery.

That came after a report by Daily NK, a South Korea-based news outlet specializing in North Korea issues, that Kim Jong-un was receiving medical treatment outside Pyongyang following a cardiovascular procedure, said the Yonhap News Agency.

The Minister during Tuesday's briefing called those reports "fake news" based on unconfirmed information.