Two North Korean defectors who served in senior positions in the government in Pyongyang appeared before a Congressional panel Tuesday to discuss their roles in that country's missile program and in state-sponsored drug trafficking.

The two men were led into the hearing room wearing hoods, and then testified behind a screen to hide their identities. They spoke through an interpretor. The men, who now live in South Korea, were brought to the United States by two refugee advocacy groups.

One of the men worked as a missile scientist from 1988 to 1997, the year he defected. He testified about his role in Pyongyang's budding program to export missile technology. The missile scientist said in 1989, he was ordered to go to Nampo seaport to board a freighter for what turned out to be a two week trip. When the ship docked, he was taken aboard a missile guidance control vehicle with curtained windows on a two-day trip to a remote location, where he and a small team of scientists activated and fired a missile.

Upon his return to Nampo, the missile scientist was told by a senior North Korean official that his mission had been to Iran. After that trip, he said his plant continued to manufacture missile control vehicles. "After our trip, sub-plant 603 and 604 began producing the same missile guidance control vehicles as we took to Iran," he said. "Since then, we produced nine such vehicles over a few years, and exported them to Arab countries." He said that 90 percent of the components used in his work inside the North Korean missile project were smuggled in on ferry services from Japan, every two or three weeks.

The other defector, who left North Korea in 1998, worked for a North Korean government agency for 15 years. He testified about state-sponsored drug production and trafficking as a way for North Korea to earn hard currency.

He said after poppies are harvested from the fields, they are sent to a factory to be processed into heroin: "They are processed and refined into heroin under the supervision of seven to eight drug experts from Thailand, and this is all done under the direct control and supervision of the central government," he said.

The defector also talked about North Korea's lucrative drug trafficking activities. "In China near the border, the drugs are sold for $10,000 per kilogram, and through the ocean border, these drugs are sold for $15,000 per kilogram," he said. "North Korea sells these drugs through the border with China or through the seas, Hong Kong, Macau, Russia, Japan, even South Korea. They also deal with international drug dealers in the Yellow Sea."

The defector said North Korea is the only country on earth that grows poppies, processes it into heroin, and sells it abroad. He said North Korean diplomats often work as drug traffickers.

Earlier, Mr. William Bach of the State Department's Bureau of International Narcotics and Law Enforcement Affairs said since 1976, more than 50 North Koreans have been arrested in connection with drug seizures in more than 20 countries around the world.

Just last month, Australian police arrested 26 crew members of a North Korean ship who were trying to offload some $80 million worth of heroin on to a fishing boat near the Australian coast. One of the crew has been identified as a senior member of North Korea's Workers' Party.