Parties linked to underworld syndicates will be prohibited starting June 1 from sponsoring foreigners coming into Japan on entertainer visas, the Justice Ministry announced in its public bulletin Monday.

The move, stipulated in an amended ministerial ordinance, is aimed at curbing human-trafficking. Foreign women who have entered Japan on "entertainer" visas, ostensibly as singers or dancers, have often been forced to work as hostesses in low-paying bars or nightclubs or to engage in prostitution.

Under the new ordinance, companies linked to the yakuza or people who were members of such groups in the past five years will not be allowed to sponsor foreign entertainers.

When sponsoring entertainers, companies also will be required to offer contracts paying the workers more than 200,000 yen per month.