An Indian court has sentenced four men to life in jail for gang-raping a woman in Mumbai last year.

The men had been convicted by the same court a day earlier for gang-raping two women in the abandoned Shakti Mills compound in two separate incidents.

Friday's life sentences were over the rape of a telephone operator. The court will pronounce the punishment over the gang-rape of a woman photojournalist at the same place next week.

The sexual assault on the photojournalist in August while she was on an assignment triggered outrage across the nation.

A few days later, the telephone operator lodged a complaint with the police, saying she too had been raped by the men in July.

A recent string of sex crimes have sent shockwaves across the country, forcing the federal government to bring about stricter laws.

A month ago, a woman in the eastern state of West Bengal was gang-raped as punishment on the orders of a village court after she was found with her boyfriend.