New Delhi, March 10 -- Sunday's marches in Brazil for International Women's Day served as a rallying cry against gender-based violence, fueled by the latest case to outrage the country involving the alleged gang rape of a 17-year-old girl in Copacabana.

The case in Rio de Janeiro's famed, beachside neighborhood took place in January, but gained national traction this week when four suspects handed themselves over to authorities. Described by police as a gang rape, it has added fuel to the fire in a nation where reports of violence against women have surged in recent months, sparking nationwide protests and a flurry of digital activism.

At least 15 protests were planned across the country, with organizers calling for the defense of women...