SEOUL (AFP) - A huge explosion rocked North Korea`s northern inland province of Ryanggang last week, triggering a mushroom cloud at least two miles in radius, South Korea`s Yonhap news agency said.
The explosion appeared to be stronger than an April 22 blast that killed more than 150 people and wounded some 1,300 others in Ryongchon near the western tip of North Korea`s border with China, it said Sunday.
The latest blast took place in Kimhyungjik county near the Chinese border on September 9, when North Korea marked the 56th anniversary of its founding, Yonhap said, citing unnamed sources in Beijing.
"The United States was known to have shown its keen interest in the explosion after spotting its traces by satellite," the source was quoted as saying.
South Korea`s unification minister Chung Dong-Young said Seoul had received an unsubstantiated report on the explosion in North Korea.
"We have received an unsubstantiated report on traces of an explosion in North Korea," he told reporters after a meeting of security-related officials. The unnamed source in Beijing said the blast had prompted speculation in Washington that the explosion was possibly related to a nuclear experiment, it said.
Chung, however, played down the possibility of a North Korea`s nuclear weapons test.
He said the South Korean government was not aware of the scale of the blast but Yonhap quoted a diplomatic source in Seoul as saying the blast triggered a mushroom cloud with a radius of 3.5 to four kilometers (2.4 miles).
"The explosion occurred at around 11 am. But it is not clear yet whether the explosion is related to an intentional nuclear experiment or a simple accident," he was quoted as saying.
He noted the site of the explosion was not far from the North`s missile base, according to Yonhap.
The New York Times reported on its Web site Saturday that US President George W. Bush and his top advisers have received intelligence reports describing a confusing series of actions by North Korea that some experts believe could indicate the country is preparing to conduct its first nuclear weapons test.
Citing unnamed senior officials with access to intelligence, the newspaper said US intelligence agencies appeared 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.
US 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.