Women sewing blue jeans for Levi's, Wrangler, Lee and The Children's Place faced sexual harassment and gender-based violence and some were coerced into having sex with supervisors to keep their jobs in African factories, labor rights groups say.

In response to the revelations, the brands have agreed to bring in outside oversight and enforcement for more than 10,000 workers at five Lesotho factories, according to a report from the Washington-based Worker Rights Consortium released on Thursday.

The labor rights group investigated Taiwan-based Nien Hsing Textile factories in Lesotho — a poor, mountainous kingdom encircled by South Africa — after hearing from a number of sources that women who sew, sand, wash and add rivets to blue jeans and other clothes were facing gender-based violence.

Managers and supervisors forced many female workers into sexual relationships in exchange for job security or promotions, the report says. In dozens of interviews, the women described a pattern of abuse and harassment, including inappropriate touching, sexual demands and crude comments...