Yoshifumi Yoshihara, a 45 year-old trader, and Ri Yong Sun, 52, a female North Korean living in Japan, were convicted of exporting merchandise without authorisation, said presiding judge Shoichi Matsuo at the Yokohama District Court.

Yoshihara received a one-year prison term, suspended for three years, while Ri received a 10-month term, suspended for three years.

The two shipped an inverter for an industrial washing machine last November from Japan for a final destination in North Korea but the equipment was sent back by a trading company in Beijing last month, according to court documents.

"They exported it, despite knowing full well that they did not have a permit to export it," the judge said.

The inverter could be converted for military use to become part of the process to enrich uranium, police said earlier.

The Yokohama customs office rejected an application from Yoshihara for the shipment of the Japanese-made inverter to North Korea in August.

Yoshihara and Ri, who has a relative in North Korea, then shipped the equipment without authorisation.

In 2002, Japan introduced export regulations that require government approval for all exports that could be used for developing weapons of mass destruction.

Last October, Japan, and seven other Asia-Pacific economies, the United States, China, South Korea, Australia, Singapore, Thailand and Hong Kong, agreed to cooperate in blocking such exports, particularly to North Korea.

Illegal exports to North Korea from Japan have been made more difficult in recent years following a series of crackdowns but many Asian nations still have loose export controls.

WAR.WIRE