The US government said today that the test conducted by North Korea on October 9th was a nuclear explosion of less than one kiloton.
"Analysis of air samples collected on October 11th, 2006, detected radioactive debris which confirms that North Korea conducted an underground nuclear explosion," the director of national intelligence said in a statement.
The statement said the explosion yield was less than a kiloton. By comparison, the nuclear bomb the United States dropped on Hiroshima, Japan, in 1945 was about 12.5 kilotons.
The announcement last week by the reclusive communist state that it had tested a nuclear bomb sharply escalated world concerns over North Korea's nuclear program.
China today inspected North Korea cargo trucks bound for its communist ally and stepped up construction of a border fence. The Chinese inspections at a border crossing with the North came amid concerns that Beijing would ignore the new UN sanctions levelled against North Korea.
China is a major trader with North Korea, and its support is key to the success of the new UN measures, which call for nations to check cargo leaving and arriving from North Korea.
Chinese customs inspectors examined cargo trucks bound for the North in the border city of Dandong. The officers opened the back of each truck and looked at its cargo, though they did not open individual containers.
Last week, reporters who visited the border post did not see inspectors open any trucks.
In a further sign of fraying ties between China and North Korea, the Chinese have been building a massive barbed wire and concrete fence along parts of its border with the North.
Although the project was approved in 2003, the fence-building appears to have picked up since the test was announced.
Japan - once a major trading partner with the North Korea - said it was considering further sanctions, and Australia has banned the North's ships from its ports.
South Korea called today for Russia to play an active role in resolving the nuclear standoff with North Korea.
AP