US President Donald Trump said on Monday he has a good idea how Kim Jong-un is doing and hopes he is fine, after days of speculation over the North Korean leader’s health.

Kim’s whereabouts and whether he had a heart procedure have been a subject ofspeculation in recent weeks.

Daily NK, a Seoul-based website, reported last week that 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 Kim was spotted last week at the North Korean resort town of Wonsan, according to satellite images.

“I can’t tell you exactly,” Trump said when asked about 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.” Trump said it would be solved soon.

“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,” Trump said.