A scene of sexual harassment in subway from Korean movie "Sex is Zero.

A law passed by the state legislature and signed by Rio Gov. Rosinha Matheus last month obliged the underground Metro and above-ground railways to have separate passenger cars for women during the weekday rush hours.

"It's the first day today and we had women applauding when men, who had entered their carriage without knowing about the rule, got off," a spokeswoman for the private Metro Rio company said.

Frequent complaints from women commuters about sexual harassment in crowded railway cars had prompted state legislators to pass the bill.

One car in every of Metro Rio's 33 trains is marked with pink stripes on doors and windows. The company said female passengers would themselves control men's entry into the cars, seeking the help of security guards if necessary.

Railroad company Supervia, which serves Rio and its suburbs, identifies its female-only cars with signs similar to those on women's restrooms.

Men won't be barred from the female-only cars during an initial phase but after that railroad police would enforce the new rule, a Supervia spokesman said.

Rio joins Tokyo and Mexico City as major cities that provide female-only train cars.