China's official Xinhua news agency confirmed that Kim was visiting from Monday to Thursday at Xi's invitation.
Discussions between the United States and North Korea over Pyongyang's nuclear arsenal have stalled since Kim and Trump's high-profile summit in Singapore in June where they issued a vaguely worded declaration about denuclearisation.
"We will not loosen our guard until the promise to denuclearize the Peninsula is kept, and peace is fully institutionalized", added Moon.
"The Korean peninsula situation has been easing since past year, and China's important role in this process is obvious to all ... the DPRK side highly and sincerely appreciates the Chinese efforts", Kim said.
Moon's overture, however, has invited criticism from conservatives in South Korea and the United States that he's making too many concessions and helping the North weaken USA -led sanctions.
"China has always supported both sides to continue to hold talks and to reach a positive outcome", Lu said.
Mr Xi said China supported North Korea and the United States "holding summits and achieving results, and supports relevant parties resolving their respective legitimate concerns through dialogue".
His visit was also seen as part of an effort to win Chinese support for a reduction of United Nations sanctions imposed over his nuclear weapons and ballistic missile programs, which have severely impacted his country's already ailing economy. The North Korean leader said in his New Year's address that he might take a "new path" in negotiations if Trump didn't ease trade, travel and investment restrictions.
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Mr Moon said North Korea should take more concrete steps, such as abandoning its intercontinental and intermediate-range ballistic missiles and dismantling weapons production lines and other nuclear complexes, to secure USA concessions such as sanctions relief.
Kim's visit comes as a USA delegation opened a second day of talks with Chinese counterparts in Beijing aimed at ending the trade war between the world's two largest economies. Mr. Kim was accompanied by his wife, Ri Sol Ju, the news agency said.
North Korea will 'make efforts for the second summit to achieve results that will be welcomed by the worldwide community, ' Kim was quoted as saying by China's official Xinhua News Agency.
The massive plant is owned by Tong Ren Tang (同仁堂), the world's top producer of traditional Chinese medicines with a history that dates back more than three centuries.
It said he met with Xi at the Great Hall of the People on Tuesday after a welcoming ceremony.
Moon, however, made it clear that North Korea taking denuclearization steps is the key to resolving the matter.
Each of the previous Kim-Xi meetings have come shortly before or after the North Korean's summits with either Trump or South Korean President Moon Jae-in.
However, a meeting between Mr Pompeo and senior North Korean official Kim Yong Chol has yet to be rescheduled after an abrupt cancellation in November.
Mr Kim told Mr Xi about the difficulties and concerns in improving North Korea-US relations and denuclearisation negotiations, KCNA said.