The men, who gave evidence behind a screen to conceal their identities, after being led into the hearing room wearing black hoods, now live in South Korea, but were brought to the United States by two refugee advocacy groups.

Their appearance came as the Bush administration tries to turn the spotlight on North Korea's alleged criminal behavior after making little obvious progress to end a simmering crisis over the communist state's nuclear weapons programs.

Journalists and members of the public were asked to leave a three-hour hearing of a subcommitee of the Republican controlled Senate governmental affairs committee for a final classified session in which the men promised to divulge highly sensitive data.

But one witness, using the alias Bok Koo Lee told the open portion of the hearing that he worked as a missile scientist for nearly nine years at Plant 39 in Huichon, Jagang Province, North Korea before defecting in July 1997.

He said in summer 1989 he became an unwitting pawn in Pyongyang's nascent missile technology export plans.

Bok said he was ordered to go to Nampo seaport, dressed in military fatigues and locked inside a freighter for a sea voyage of around 15 days.

When the ship docked, he was taken aboard a missile guidance control vehicle with curtained windows on a two-day journey to a secret location.

"Although it was night-time, we could see and immediately we realized that we were in a Middle Eastern country, judging by a foreign soldier and his physical makeup," Bok said.

The small team of scientists activated and fired the missile from a remote site, before immediately being returned to the ship for a 15-day journey back to North Korea locked in the hold.

During a visit to Pyongyang on his return, Bok said he was told by senior North Korean officials that his mission had been to Iran, and testified that his plant subsequently churned out more of the missile control vehicles he had worked on during the project.

Bok alleged that 90 percent of components used in his work inside the North Korean missile project were smuggled in on scheduled ferry services from Japan, every two of three weeks.

His compatriot, identified only as defector number one said he was a former high-level government official in the Stalinist state.

"North Korea must be the only country on earth to run a drug production-trafficking business, on a state level," he said.

He alleged that Kim Jong-Il's regime, desperate for hard currency, produced large quantities of heroin and methamphetamines.

Opium was sent to a pharmaceutical plant in Chungjin city, and "processed and refined into heroin under the supervision of seven to eight drug experts from Thailand," he said.

"This is all done under the direct control and supervision of the central government."

SPACE.WIRE