Intelligence agencies have warned that satellites have detected suspicious movements near the 9 October nuclear test site in North Korea, immediately sparking fears that a second nuclear test was pending.

|PIC1|US Secretary of State Condoleezza Rice has warned North Korea that a second nuclear test would be a provocative act that could only deepen its isolation. Rice spoke as she prepared for a tour of Asia to strengthen the sanctions the UN has imposed on North Korea.

The US has said that it has detected movement at last week's test site but cannot confirm if it points to a second test.

In addition, US intelligence officials said on Monday that air samples had confirmed the blast on 9 October was nuclear.

Last week the UN Security Council unanimously voted to impose sanctions, targeted at North Korea's weapons and missile programmes.

Rice said, "We expect every member of the international community to fully implement all aspects of this resolution. And we expect the Security Council to aggressively monitor the process. As North Korea scorns the international community, we will collectively isolate North Korea from the benefits of participation in that community."

She warned that a second test by the North would "further deepen the isolation of North Korea and I hope they would not take such a provocative act".

Japanese Foreign Minister Taro Aso said on Tuesday Tthat Tokyo was aware of the reports of activity at the test site, but said he could not disclose details.

South Korea has also said it was analysing the intelligence reports.

US Director of National Intelligence John Negroponte said on Monday findings had shown North Korea did carry out a nuclear explosion a week ago. The small size of the explosion had led to doubts over the reliability of North Korea's claim. However, the short statement from Negroponte's office confirmed that a nuclear explosion with a yield of "less than a kiloton" took place.

This is less than a tenth of the size of the bomb dropped on Hiroshima in 1945.