Kim's return to Pyongyang marked the end of a marathon 4,000-kilometre (2,500-mile) journey from Vietnam, where his much-hyped second summit with Trump came to an abrupt halt last week.

That was followed by an official visit to the country, where Kim paid tribute to Vietnam's late revolutionary leader Ho Chi Minh.

"Kim Jong Un... arrived at home on Tuesday after successfully wrapping up his official goodwill visit to the Socialist Republic of Vietnam," the official KCNA news agency said.

"At 3 o'clock in the early morning, his train entered the railway station yard" in Pyongyang, it added.

Kim has visited China, the North's key diplomatic protector and main provider of trade and aid, four times, and it had been thought he may have made a stop in Beijing to see President Xi Jinping.

Talks between Kim and Trump in Hanoi finished abruptly, with a signing ceremony scrapped after the pair failed to reach an agreement on walking back North Korea's nuclear programme in exchange for sanctions relief.