SEOUL, Oct 3: UN nuclear watchdog chief Mohamed ElBaradei said on Sunday he wants South Korea to come clean about past unauthorized nuclear experiments and not to repeat its mistake.

ElBaradei, director general of the International Atomic Energy Agency (IAEA), arrived in South Korea as his agency was investigating Seoul's secret experiments with potential ingredients for atomic bombs.

"Any undeclared activities is a matter of serious concern for me," said ElBaradei who flew in Seoul to attend a conference. "We just wanted to make sure these were experiments and that there were nothing more than these experiments ... (and that) these experiments will not be repeated again without being declared to the organization."

But he warned against any hasty judgement on South Korea. "You cannot speculate on the issue before we have a comprehensive report on these experiments," he said. IAEA inspectors last month visited the country to investigate Seoul's shock revelations of past secret experiments with plutonium and enriched uranium which can be used for nuclear bombs.

South Korea disclosed in September that its scientists secretly enriched a tiny amount of plutonium in 1982 and uranium in 2000. Foreign Minister Ban Ki-Moon reiterated on Sunday the lab experiments had been purely for scientific purposes, not linked to nuclear weapons programmes.

"I expect a fair and objective conclusion based on facts to be presented before the board of governors on November 25," Ban told ElBaradei at a meeting late on Sunday.

ElBaradei is to hold a series of meetings with other top South Korean leaders, including Prime Minister Lee Hae-Chan on Monday and Unification Minister Chung Dong-Young on Tuesday.

The case has embarrassed the United States and South Korea when they are trying, through six-party talks, to pressure North Korea to end its nuclear weapons drive.

The North has refused to take part in a fourth round of the multilateral talks, blaming what it calls hostile US policy and the secret nuclear experiments. ElBaradei, who is being tipped as a possible Nobel Peace Prize winner, travels on Wednesday to Japan.

The prize winner is to be announced on Friday in Oslo. Observers have said they expect the Nobel committee this year to hail efforts to halt the spread of nuclear weapons. -AFP