Mohamed ElBaradei, head of the International Atomic Energy Agency (IAEA), left Pyongyang on Wednesday afternoon for Beijing after winding up a two-day visit to the Democratic People's Republic of Korea (DPRK).
Before his departure, ElBaradei declined to answer any questions from reporters and said only that he would release relevant information in Beijing.
Staff at Pyongyang Sun-an airport told Xinhua that the IAEA chief's plane took off one hour earlier than previously scheduled.
The DPRK expelled IAEA nuclear inspectors in December 2002, and in January 2003, the country announced its withdrawal from the nuclear Non-Proliferation Treaty (NPT).
During last month's six-nation talks in Beijing, the DPRK agreed to give up its nuclear weapons program, and shut down its Yongbyon nuclear facilities by mid-April.
Soon after the talks in Beijing, the UN nuclear chief said on Feb. 23 that the DPRK had invited him to visit within the next few weeks for talks on its nuclear program.
The IAEA delegation headed by ElBaradei arrived in Pyongyang on Tuesday.