File photo of Chinese railway police guarding the platform as a passenger train from North Korea pulls into Dandong station in this border town in northeast Liaoning Province. (AFP PHOTO/Frederic J. BROWN)
The North's leader, accompanied by his wife Ri Sol Ju and several senior officials set off from Pyongyang station on board his private train on Monday, the Korean Central News Agency reported.
China's official Xinhua news agency also confirmed the visit.
The trip is at Xi's invitation and set to run over four days, KCNA added, with Kim slated to return on Thursday.
The visit is likely to heighten speculation about a potential second summit between Kim and US President Donald Trump.
Kim visited China three times last year.