The train arrived in the border city of Dandong after 9pm local time, according to South Korea’s Yonhap news agency and the specialist outlet NK News, though it was not known whether Kim was on on board.
The train’s crossing into China follows days of speculation over Kim’s travel plans, which remain shrouded in secrecy, as his team gathered in Hanoi ahead of the talks expected next Wednesday and Thursday.
Security was tight before the train’s arrival, with police cordoning off the riverfront some 100 metres (yards) from the bridge with tape and metal barriers, and leading a journalist out of the area.
Guests at a hotel facing the rail bridge from North Korea were suddenly asked to leave on Friday and told it was closed Saturday for impromptu renovations.
“The train is long and crossed the bridge slower than the tourist train, but its definitely him, there’s a lot of police presence,” an unidentified source told NK News.
Windows on the train were blacked out, the source said, with only headlights turned on as it crossed.
Kim has previously travelled in an armoured train to Beijing and, if he is on board, may stop in the Chinese capital on what could be an epic journey to Vietnam, meeting President Xi Jinping prior to his second face-to-face with the US president. Or he could save the meeting for his return trip to debrief his country’s sole major ally.
Trump and Kim met in June in Singapore, producing a vaguely worded agreement on denuclearisation, but progress has since stalled, with the two sides disagreeing over what the agreement meant.
Observers say tangible progress is needed in Hanoi to avoid the talks being dismissed as a publicity stunt.
Kim travelled to Singapore last year on a plane lent by Beijing, and it remained unclear whether he would ride all the way to Hanoi by rail — a nearly 4,000-kilometre journey taking more than 60 hours from Pyongyang.
Another option would be to take the train to Beijing and catch a plane to the Vietnamese capital.
But several sources said Kim was expected to arrive in Vietnam by train, stopping at the Dong Dang train station near the China border, then driving to Hanoi.
On Saturday soldiers were deployed to Dong Dang station and along the road to the capital, according to reporters at the scene.
It came after Vietnam announced the unprecedented move of closing that 170-kilometre stretch of road on Tuesday between 6am and 2pm — suggesting Kim could travel on the road between those hours.
The Vietnamese foreign ministry said that Kim would “pay an official visit to Vietnam in the coming days”. He is expected to tack on a visit to industrial zones in Vietnam’s Quang Ninh and Bac Ninh provinces, sources said.