Mr Kim was quoted as saying he had 'successful talks' with Xi Jinping
North Korean leader Kim Jong Un has visited China in his first foreign trip since taking power, it has been confirmed following much speculation.
The head of the secretive regime has been in the capital Beijing for historic talks with the country's President Xi Jinping.
The trip, which lasted several days, comes ahead of planned summits between North Korea, South Korea, and the US - with the three having agreed to talk to allay tensions over Mr Kim's nuclear ambitions.
Mr Xi hosted a banquet for him and his wife Ri Sol Ju, according to China's official Xinhua news agency, which reported Mr Kim as saying he was "committed to denuclearisation".
Mr Kim was quoted as saying: "I have had successful talks with General-Secretary Xi Jinping on developing relations between the two parties and the two countries, our respective domestic situation, maintaining peace and stability on the Korean Peninsula, and other issues."
Mr Kim also said Pyongyang was "determined" to improve ties with South Korea and "willing" to hold a summit with the US.
The North Korean leader visited China - his country's closest ally - between Sunday and Wednesday, with President Xi accepting an invitation to make a return visit "at a convenient time".
It was Mr Kim's first overseas trip since becoming leader in 2011, which the White House said was "further evidence that our campaign of maximum pressure is creating the appropriate atmosphere for dialogue".
"The Chinese government contacted the White House earlier on Tuesday to brief us on Kim Jong Un's visit to Beijing," a spokesman added.
"The briefing included a personal message from President Xi to President Trump, which has been conveyed to President Trump. The United States remains in close contact with our allies South Korea and Japan."
Speculation had been growing on Tuesday that Mr Kim, whose regime has carried out a series of nuclear missile tests in recent years, was in Beijing after a diplomatic train arrived from Pyongyang.
The train was met with tight security when it rolled into the Chinese capital, and a convoy of 20 cars was seen leaving the city's Diaoyutai State Guest House, where senior foreign leaders often stay during visits.
Police blocked roads near the building as the convoy travelled by.
Heavy security was reported at the Friendship Bridge over the Yalu River which marks the border between China and North Korea before a train passed. The train has since left Beijing's station.
Yoo Ho-yeol, a professor of North Korean studies at Korea University in Seoul, suggested the meeting was likely a bid by Mr Kim to "reaffirm close ties" with Beijing before a planned summit with US President Donald Trump.
He said: "If North Korea speaks with the US on its own it might feel it is at a disadvantage, but if it has China as an ally, Pyongyang may think it will be able to protect its interests and profits during the summits."
The leader's sister, Kim Yo Jong, who some analysts have suggested could have also been aboard the train, visited the South for the Winter Olympics in February, and earlier this month senior officials from Seoul travelled to Pyongyang.
Mr Trump has since agreed to meet Mr Kim by May, with the latter's foreign minister's recent visit to Sweden fueling suggestions that the historic summit could take place in the country.
Mr Kim's father, Kim Jong Il, last visited Beijing in 2011 and did so aboard a train similar to the one spotted in the city on Monday.