Choe Ryong Hae, vice marshal of the Korean People's Army, met with Wang Jiarui, a senior official of the Chinese Communist Party, The Washington Post reported, citing China's Xinhua news agency.
Neither Pyongyang nor Beijing indicated the length of Choe's stay, details of the meeting or the purpose of the visit.
It was the first visit by any top North Korean official since August 2012 and comes after some apparent differences between the neighboring countries have been subjects of public analysis.
Beijing had warned Pyongyang not to carry out a nuclear test in February and supported United Nations sanctions imposed after North Korea ignored the advice.
North Korea recently seized the crew of a Chinese fishing boat, holding the crewmen for two weeks in a demand for ransom, while the Bank of China earlier this month cut off dealings with a North Korean bank used to fund Pyongyang's weapons program.
Choe is one of the North Korean leader's top lieutenants. Since Kim took power, Choe has been showered with a number of high-profile titles that have given him power comparable to that of Kim's aunt and uncle.