Kim Yong-chol, a former spy chief, arrives at Beijing airport and is booked to leave on a flight for Washington later in the day, South Korea's Yonhap news agency says.
A senior North Korean official arrived in Beijing on Thursday, reportedly en route to the United States for talks ahead of a possible second summit between President Donald Trump and North Korean leader Kim Jong Un.
Kim Yong-chol, a former spy chief, arrived at Beijing airport and was booked to leave on a flight for Washington with two other North Korean officials later in the day, South Korea's Yonhap news agency said.
A motorcade that included the North Korean ambassador's car and a Chinese car with a sign reading "state guest" could be seen departing from a VIP area at the airport.
Neither the US nor North Korea has announced any meetings.
Kim Yong-chol has been holding talks with US Secretary of State Mike Pompeo on North Korea's nuclear weapons programme and related issues.
A planned meeting between the two in New York last November was called off abruptly. US officials said at the time that North Korea had cancelled the talks.