SEOUL (REUTERS) - North Korea on Sunday (Feb 24) confirmed for the first time that its leader Kim Jong Un will hold a second summit with United States President Donald Trump, days ahead of the high-stakes nuclear meeting set to take place in Vietnam's capital of Hanoi.

Mr Kim left Pyongyang by train on Saturday afternoon for this Wednesday and Thursday's summit, accompanied by senior North Korean officials, North Korea's official KCNA news agency and its Rodong Sinmun newspaper reported.

In rare, revealing coverage of Mr Kim's travel, while it is still going on, Rodong featured photographs of Mr Kim getting a red-carpet honour-guard send-off in Pyongyang and waving from a train carriage door while holding a cigarette.

The delegation with Mr Kim includes top North Korean officials who took part in last year's expanded summit talks between Mr Kim and Mr Trump in Singapore, including top envoy to the US, Mr Kim Yong Chol, vice-chairman of the central committee of North Korea's Workers' Party Ri Su Yong, and foreign minister Ri Yong Ho.

The North Korean leader's sister, Ms Kim Yo Jong, who was also seen aiding him in Singapore, is travelling with him as well.

Other senior North Korean officials, such as his de facto chief of staff Kim Chang Son, and Mr Kim Hyok Chol, who is the negotiations counterpart to US special envoy Stephen Biegun, are already in Hanoi to prepare for the summit.

Mr Kim Jong Un will also make an official goodwill visit to Vietnam "soon", KCNA said.

The extensive coverage in the secretive North's official media was a contrast to the limited reporting that has traditionally prevailed during his foreign trips.

On Saturday, Vietnam's foreign ministry announced that Mr Kim would make an official visit to Vietnam in the "coming days", at the invitation of Mr Nguyen Phu Trong, the president and general secretary of its ruling Communist Party.

Few details of summit arrangements have been released.

Some lamp posts on Hanoi's tree-lined streets are decked with North Korean, US and Vietnamese flags fluttering above a handshake design, and security has been stepped up at locations that might be a summit venue, or where the leaders might stay.

Vietnamese media reported that a North Korean cargo plane arrived on Sunday carrying personnel who appeared to be Mr Kim's security guards and state media workers. They were driven under police escort to a downtown hotel.

Mr Trump and Mr Kim will meet in Hanoi eight months after their historic summit in Singapore, the first between a sitting US president and a North Korean leader, where they pledged to work toward the complete denuclearisation of the Korean peninsula.

But scant progress since then has driven the two leaders to again seek a top-down approach to diplomacy, analysts said.

"They will not make an agreement which breaks up the current flow of diplomacy. (President Trump) has mentioned that they'll meet again; even if there is a low-level agreement, they will seek to keep things moving," said Mr Shin Beom-chul, a senior fellow at the Asan Institute for Policy Studies.

The Trump administration has pressed North Korea to give up its nuclear weapons programme, which threatens the US, before it can expect any concessions.

North Korea wants an easing of punishing US-led sanctions, security guarantees and a formal end of the 1950-1953 Korean War, which ended in a truce, not a treaty.

Both sides are under pressure to forge more specific agreements than were reached at the Singapore summit, which critics, especially in the US, said lacked detail.

If Mr Kim travels all the way to Vietnam by train he could take at least 2½ days to make the journey of thousands of kilometres through China.

Beijing has given no details of Mr Kim's trip through China. On Sunday, its foreign ministry did not immediately respond to a request for comment on whether Mr Kim would meet President Xi Jinping before arriving in Hanoi.

On Tuesday, Vietnam will ban traffic on the road Mr Kim is expected to take to Hanoi from a station on the Chinese border, state media said.

Travel by train has been a favourite mode of transport for Mr Kim, as it was for his father Kim Jong Il, and grandfather Kim Il Sung.

When Mr Kim Il Sung visited Hanoi in 1958, he travelled from Pyongyang to Beijing and then southern Guangzhou by train, finally flying to Hanoi in an aircraft provided by China, its state-run Global Times said on Sunday.