Those arrested are the president and officials of a Tokyo machine manufacturing firm who are being held on suspicion of "exporting strategic equipment without government authorisation," a spokesman for the Metropolitan Police Department said.

The company, Seishin Enterprise Co. Ltd., was suspected of exporting two jet mill grinders in 1999 and 2000 to military-related companies for "several tens of millions of yen," the spokesman said.

Ten million yen is worth some 84,000 US dollars.

The jet mill grinds solid substances into superfine powder and it can be used to pulverise materials for solid fuel for missiles.

The spokesman, however, could not confirm a press report that Seishin had also exported a jet mill to North Korea in 1994.

The Jiji Press news agency reported that the jet mill was shipped to a firm affiliated to North Korea's defence ministry.

The jet mill is on the list of restricted items of the Missile Technology Control Regime (MTCR), an international mechanism to curb exports of missiles as well as missile-linked equipment and technologies.

The regime specially enforces tight controls on exports to Iran, Iraq, North Korea and Libya. Iran, Iraq and North Korea have been branded by US President George W. Bush as an "axis of evil" bent on spreading weapons of mass destruction.

Japan's trade controls law lists the jet mill along with such items as rocket launchers as strategic goods that require approval from the trade minister for export.

The arrested were Seishin's founder and president Haruhiko Ueda, 68, Seishin's technical development director Hitoshi Ito, 54, and the company's manager in Seoul Akira Kamiya, 41, as well as overseas business chief, Eri Tanemura, 29, and a regional branch manager, Toshitaka Matsuda, 42.

SPACE.WIRE