A United States court in Hawaii has sentenced the Korean owner of a sweatshop factory to 40 years in jail, the most severe punishment ever imposed in a human trafficking case.

Prosecutors called it the biggest case ever of "modern day slavery" and said that the tough sentence was justified. "Justice was served, and we're glad the victims are safe," said prosecutor Robert Moossy.

The U.S. Justice Department said Lee Soo-Kil held more than 300 victims from China and Vietnam as forced labourers in involuntary servitude at his garment factory in American Samoa.

He's accused of using arrests, forced deportations and brutal physical beatings to keep workers under control.

The court was told that he ordered a worker to gouge the eye of another worker who dared to complain about her living and working conditions.

The workers were recruited from China and state-owned labour export companies in Vietnam, and each had paid a fee of up to $5,000 US to get a job at Daewoosa Samoa Ltd. in Pago Pago.

About 200 of the workers have been allowed to remain in the United States. Approximately 100 others have opted to return to their homes.

with files from the Australian Broadcasting Corporation