SEOUL - UN Secretary-General Ban Ki-moon will visit Democratic People's Republic of Korea (DPRK)'s capital Pyongyang this week, South Korea's Yonhap news agency reported on Monday, quoting a U.N. source, in what could be a rare diplomatic opening by the isolated state.

Ban, who is South Korean, had earlier this year made plans to visit the North, but Pyongyang retracted the approval for the trip at the last minute without explanation.

"It is impossible that the U.N Secretary-General will not meet the leader of DPRK, a UN member state, as he visits the country," the source told Yonhap, adding that the trip would likely provide significant momentum to resolve issues on the Korean Peninsula.

The Democratic People's Republic of Korea is under heavy UN, EU and US sanctions for its missile and nuclear tests.

South Korea's foreign ministry could not immediately confirm the report. Yonhap did not have further details about the trip.

The U.N. spokesman's office had no immediate comment.

Two serving UN chiefs have visited the North previously.

Kurt Waldheim visited Pyongyang in 1979 and again in 1981. Boutros Boutros-Ghali visited in 1993.

Ban served as South Korea's foreign minister from 2004 to 2006, a period of intense multinational negotiations aimed at ending the North's nuclear programme. Those talks led to a 2005 deal that later fell apart.