WASHINGTON (REUTERS) - US President Donald Trump said on Monday (April 27) he knows how Kim Jong Un is doing and hopes he is fine, after days of speculation over the North Korean leader's health.

Mr Kim’s whereabouts and whether he had a heart procedure have been a subject of intense speculation in recent weeks.

Daily NK, a Seoul-based website, reported last week that Mr Kim was recovering after undergoing a cardiovascular procedure on April 12, citing one unnamed source in North Korea. Reuters has not been able to confirm the report.

A special train possibly belonging to Mr Kim was spotted last week at the North Korean resort town of Wonsan, according to satellite images reviewed by 38 North, a Washington-based North Korea monitoring project.

"I can't tell you exactly," Mr Trump said when asked about Mr Kim's condition at a White House news conference.

"Yes, I do have a very good idea, but I can't talk about it now. I just wish him well."

"I hope he's fine. I do know how he's doing relatively speaking. We will see - you'll probably be hearing in the not too distant future," Mr Trump said.

Rumours and speculation over Mr Kim's health began after he did not appear in public at a key state holiday on April 15. He has since remained out of sight.

South Korean officials have emphasised they have detected no unusual movements in North Korea and caution against reports that Mr Kim may be ill or is being isolated because of coronavirus concerns.

At a closed-door forum on Sunday, South Korea's Unification Minister Kim Yeon-chul, who oversees North Korea engagement, said Seoul had the intelligence capabilities to say with confidence there were no indications of anything unusual.