Citing unnamed senior officials with access to intelligence, the newspaper said US intelligence agencies appear divided over the significance of the new North Korean actions.

The suspicious activities included the movement of materials around several suspected test sites, including one near a location where intelligence agencies reported last year that conventional explosives were being tested that could compress a plutonium core and set off a nuclear explosion, The Times said.

But officials have not seen the classic indicators of preparations at a test site, in which cables are laid to measure an explosion in a deep test pit, according to the report.

"I'm not sure you would see that in a country that has tunnels everywhere," the paper quoted one senior officials as saying.

Officials said if North Korea proceeded with a test, it would probably be with a plutonium bomb, perhaps one fabricated from the 8,000 spent nuclear fuel rods that the North has boasted in the past few months have been reprocessed into bomb fuel, the report pointed out.

However, some analysts in agencies that were the most cautious about Iraq's alleged weapons of mass destruction have cautioned that they do not believe the activity detected in North Korea in the past three weeks is necessarily the harbinger of a test, The Times reported.

Some analysts fear that a successful nuclear weapon test by North Korea could change the balance of power in Asia, perhaps leading to a new nuclear arms race there, the paper said.