RIO DE JANEIRO, March 15 (Xinhua) -- Thousands of Brazilians took to the streets of large cities on Thursday night to protest against the brutal murder of a popular Rio de Janeiro councilwoman.

Marielle Franco, an activist for human rights and women's causes, was killed along with her driver Anderson Pedro Gomes Wednesday night in downtown Rio.

The driver also died in the attack, in which their car was hit by at least nine shots after the councilwoman returned from a women's empowerment event. Franco's assistant survived the shooting with minor injuries.

The killing came just weeks after the Brazilian government decided to let the military take over all security operations in Rio to control the city's increasing crime rates. It was harshly criticized by Franco, who believed the move would worsen police violence against residents.

In Rio, a huge crowd of people marched to the Rio state assembly to protest the death of Franco, who was born and raised in the Mare slum complex, one of the most violent district in the Brazil's second largest city.

Organizers estimated that over 50,000 people participated in Rio's march. Meanwhile, protests were also staged in other state capitals, including San Paulo.

The killing of Franco, who received the fifth largest number of votes in the latest city council elections in 2016, sparked public anger on social networks. Human rights groups and the United Nations offered condolences and called for full probes.

Amnesty International and the United Nations office in Brazil hailed Franco's endeavors in defense of human rights and racism and demanded a quick and transparent investigation into the killing.