US President Donald Trump has added to the confusion about the health of North Korean leader Kim Jong-un with cryptic remarks, including that more will probably be known “in the not too distant future”.

Speculation about Mr Kim’s health began when he failed to attend commemorations for the 108th birthday of his grandfather, North Korea’s founder Kim Il-sung.

It swirled further at the weekend, with unconfirmed reports of his death or permanent incapacitation leading news bulletins across Asia.

On Tuesday (local time), Mr Trump first told a White House briefing that he had “a very good idea” about Mr Kim’s condition, only to add moments later that “nobody knows where he is.”

“I do have a very good idea, but I can’t talk about it now. I just wish him well,” he said.

“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.”

US media has reported the North Korean dictator is gravely ill, after having cardiovascular surgery.

At the weekend, Hong Kong Satellite Television, which claims to have links to a member of the reclusive nation’s ruling clan, reported a “very solid source” had confirmed the 36-year-old was dead.

The network said Mr Kim died on Saturday in a Pyongyang hospital.

In Japan, weekly news magazine Shukan Gendai quoted sources saying the North Korean dictator was as good as dead, reporting that failed heart surgery had left him in a permanent vegetative state.

Whatever the truth is, Mr Kim has not been seen in public since April 11.

Earlier, CNN reported that North Korean state media had published a letter from Mr Kim to South African President Cyril Ramaphosa, congratulating him on that country’s Freedom Day. It was dated April 27.

The network said it had no way of verifying the letter, in which Mr Kim reportedly expressed his certainty that the two nations’ friendship would continue to expand and develop.

South Korea’s Unification Minister has downplayed the speculation about Mr Kim’s health, saying there is no evidence of any “unusual developments” in North Korea.

The minister, Kim Yeon-chul, told a closed-door forum in Seoul that South Korea had “enough intelligence to confidently say that there are no unusual developments” that would back up speculation about Mr Kim’s health.

A train apparently belonging to Mr Kim has been photographed at his coastal retreat in the city of Wonsan. Researchers told CNN the train had been there since at least April 21.

-with agencies