WASHINGTON, Sept 3: An embarrassed United States called Thursday for a thorough probe into ally South Korea's secret production of enriched uranium, saying such activity should not have occurred.

The South Korean government had told the International Atomic Energy Agency in August that its scientists carried out secret experiments in enriching uranium four years ago, the agency said Thursday.

A group of IAEA inspectors went to Seoul Sunday for a week-long visit after the experiment was reported in accordance with strengthened safeguard regulations. "We expect that the agency will fully investigate the matter and keep the Board of Governors fully informed," US State Department spokesman Richard Boucher said.

"It is important that all such activity be investigated. When the investigation is complete, we and other members of the board will be able to draw the appropriate conclusions," he said. "So that needs to be done." -AFP