During his stroll, crowds yelled out Kim's name and jostled to take pictures, and the North Korean leader posed for a selfie with Singapore officials.
Shortly after a group of suited North Korean diplomats set out from their Singapore hotel on Monday for talks with US officials on the eve of a historic summit, a bigger group of North Koreans headed out in summery shirts for some shopping.
Kim is scheduled to meet with President Trump on Tuesday. The Koreans, in the North and in the South, understand that, and the inter-Korean 'Panmunjom Declaration" of 27 April focusses not on denuclearisation (although that is one of the stated goals) but on the two Koreas" "firm commitment to bring a swift end to the Cold War relic of longstanding division and confrontation", transforming the "unnatural state of armistice' into a "robust peace regime'.
The U.S. president will then address the media before flying out late Tuesday Singapore time.
Trump on Monday forecast a "nice" outcome, while Kim spent the day out of view.
Sung Kim, a USA diplomat, appears at a hotel in Singapore for working-level talks with North Korean officials on June 11, 2018.
"It's a huge win for Kim Jong Un, who now - if nothing else - has the prestige and propaganda coup of meeting one on one with the president, while armed with a nuclear deterrent", said Michael Kovrig, a northeast Asia specialist at the International Crisis Group in Washington.
Although the schedule for the summit meeting in Singapore remains flexible, two meetings between the leaders are planned.
The US President went for a lunch earlier today with Singapore's Prime Minister Lee Hsien Loong and even celebrated his birthday a couple of days early with a cake. "For the time being we can not be optimistic about the United States' behaviour, and the government of North Korea must approach this issue with absolute vigilance", he added.
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"The discussions between the United States and North Korea are ongoing and have moved more quickly than expected", the White House said in a statement.
The North Korean leader has previously drawn attention for his extreme security measures.
Trump kept open the possibility of ensuing meetings with Kim following the one in Singapore, which he said will hopefully start "something big".
Many analysts suggest Trump is perversely more at ease with traditional foes - contrasting his treatment of the likes of Canada's Justin Trudeau to the red-carpet welcome he recently gave Kim's right-hand man at the White House.
The nuclear summit carries not just high stakes for the Korean Peninsula and the fate of millions, but also Trump's own political fortunes.
Pompeo said the summit should set the framework for "the hard work that will follow", insisting that North Korea had to move toward complete, verifiable and irreversible denuclearisation. "Kim and Trump both seem to want the same thing: a dramatic reversal in the U.S".
North Korea has said it is willing to deal away its entire nuclear arsenal if the United States provides it with a reliable security assurance and other benefits.
Kim has sought to overhaul his image this year in a bid to ease global sanctions imposed after he tested nuclear bombs and long-range ballistic missiles.
In a tweet on June 1, the scholar said, "This is the only way to advance if we are to avoid catastrophic failure of diplomacy or catastrophic success, ie, offering up too much to get a deal in Singapore".