Kanagawa prefectural police official Hideshi Koshita said the three suspects, working under instruction from a North Korean trading firm based in China, were arrested Monday on suspicion of violating the Japanese foreign exchange and trade laws.

Koshita said the measuring device could be used to develop missiles and that officials were investigating the case as a possible example of arms technology links between North Korea and Myanmar _ repressive and isolated regimes, both facing international sanctions.

Police said they arrested the three suspects before a shipment.

Ri Kyong Ho, 41, a North Korean citizen living in Japan, was allegedly working under instruction from a North Korean trading company in Beijing. He allegedly conspired with Yasuhiko Muto, 57, a Japanese trading company president, and Miaki Katsuki, 75, a machinery company president, to export the device to Myanmar via Malaysia in January without seeking compulsory approval from the trade minister, the police official said.

The arrests come as the international community steps up efforts to monitor North Korea's trading practices.

A U.S. destroyer is currently tracking a North Korean freighter ship suspected of carrying banned goods off China's coast to Myanmar, in the first test of new U.N. sanctions imposed on Pyongyang's secretive regime in response to its nuclear test-blast in May.

U.S. and other officials are not sure what the Kang Nam 1 is carrying, but suspect it could be a cargo of artillery and other conventional weaponry.

North Korea is suspected to have transported banned goods to military-run Myanmar before on the Kang Nam, said Bertil Lintner, a Thailand-based North Korea expert.

Japan, a neighbor of North Korea, has intensified its suppression of illegal trade with the North, cracking down on its drug trafficking and other operations.

Last year, authorities launched a series of raids on Japanese companies suspected of making and shipping equipment used to enrich uranium for North Korea's nuclear weapons program. Japan now bans all trade with North Korea as punishment for Pyongyang's latest atomic test.