He was whisked up the lifts as his security escort of a dozen North Koreans in dark suits ran up the stairs. Up on the roof, he admired the night skyline.

The crowd waited until he came down again 15 minutes later. His contingent of body guards kept up their running pace.

Earlier Kim had posed for a selfie with Singapore’s foreign minister Vivian Balakrishnan at another tourist attraction, Gardens by the Bay.

Kim and his sister Kim Yo Jong were accompanied by a delegation of around 50 as they walked across the Jubilee Bridge on the waterfront.

South Korean media had been told Kim wanted to visit economy-related projects when he left the St Regis hotel where he is staying at around 9pm local time. It appeared the 30-something leader was also enjoying a good night out.

Rumours Kim was on the move swept through the ranks of the 2000 international media covering the summit between Kim and Trump.

Dinner plans were abandoned by reporters, including this correspondent, as they raced to likely locations for the first close up look at Kim, who had remained out of sight in the St Regis on Monday.

The Singapore-based Chosun Exchange, which runs entrepreneurship training programs for North Koreans, pointed out the Marina Bay Sands was an American brand built in Singapore by a South Korean company.

The evening tour may have been an attempt to highlight to Kim the economic benefits that could flow - with US support - if Kim agrees to give up his nuclear arsenal.

The US has offered an economic boost as a carrot to get North Korea to agree to complete and verifiable denuclearisation.

But US commentators appeared stunned and suspicious of Kim's impromptu jaunt.

NBC chief correspondent Bill Neely questioned why North Korea would give up its nuclear weapons when those weapons were the reason why he was receiving such extraordinary recognition on the world stage.

"Is this a genuine transformation; more proof of the new side of Kim Jong-un? Or is this a cyncial exploitation of his moment in the limelight where he can... fool the world into some sort of agreement while in some mountain in North Korea his scientists continue to do some [nuclear] work?" he asked.

Kim is due to meet Trump at 9am on Tuesday.