"Russia continues to support having a nuclear-free peninsula and seeks progress in the ongoing six-party talks," Medvedev said in televised comments, seated next to South Korean President Lee Myung-Bak.

Lee, who was in Moscow on a three-day official visit, said the two leaders had a "frank discussion" about Pyongyang's nuclear ambitions, which are at the centre of an international standoff.

Last week the International Atomic Energy Agency said the communist state was about to restart a nuclear reprocessing plant and South Korea warned that six-nation talks on North Korea's nuclear disarmament were near breakdown.

Russia -- a Cold War ally of communist North Korea -- is one of the five countries negotiating with Pyongyang to achieve nuclear disarmament in exchange for economic aid, along with South Korea, the United States, China and Japan.