The Xinhua news agency reported that Xi's visit on Thursday and Friday came at the invitation of North Korean leader Kim Jong Un.
But Xi had yet to reciprocate until now. Xi's visit, the first by a Chinese leader in 14 years to the internationally isolated country reeling under United Nations sanctions for pursing nuclear weapons programme, comes ahead of his proposed meeting with US President Donald Trump on the sidelines of G-20 summit scheduled to be held on June 28-29 in Tokyo.
"China-DPRK relations have opened a new chapter", state television CCTV said, adding that Mr Xi and Mr Kim have reached a "series of important consensus" (sic) in past meetings.
Chinese support was key to the effectiveness of US - and United Nations -backed sanctions of North Korea's nuclear and missile programs. The relationship is one that Chinese leader Mao Zedong once called "as close as lips and teeth".
A detachment of soldiers in white jackets was also seen outside the Liberation War Museum - which includes a section on the Chinese contribution - potentially indicating that it may be on Xi's itinerary.
"We expect the upcoming trip will contribute to an early restart of negotiations aimed at achieving complete denuclearisation of the Korean peninsula and to establishing lasting peace", said Blue House spokeswoman Ko Min-jung.
China, the North's main benefactor, has urged the two sides to return to the negotiating table after a second Trump-Kim summit collapsed in late February without a deal due to major differences over the scope of North Korea's denuclearization and potential sanctions relief by the U.S. Kim went to Russian Federation in April to meet with Putin for the first time, broadening his diplomatic horizons in his homeregion but again not signing any official agreements.More news: Fernando Alonso wins Le Mans again and World Endurance title
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In contrast, Kim Jong-un has gone to China multiple times over the past year - an unbalanced exchange that has not gone unnoticed in Pyongyang.
North Korea's official Korean Central News Agency also announced the visit, but provided no further details.
Trump has accused China of slowing down the denuclearization process with North Korea.
"They do keep score and it's like four to zero", he recently told AFP.
The visit also comes against a backdrop of tense ties between the U.S. and China with the world's two biggest economies locked in a battle over trade and technology.
Still, the nuclear situation is "under control for now", said Delury.
Mr Kim praised China's diplomatic efforts and promised the Chinese president that Pyongyang would take part in nuclear talks.