The assassination-style murder of politician and activist Marielle Franco on March 14 shocked Brazil and made headlines across the world

Rio de Janeiro (AFP) - A handful of quiet memorials took place in Rio de Janeiro Saturday remembering Marielle Franco, the black councilor gunned down a month ago in a killing that made international headlines but for which no-one has been arrested.

The 38-year-old, who was a critic of police brutality and an outspoken advocate for minorities, was shot dead on March 14 in an assassination-style killing with four bullets to the head.

At one ceremony in Largo do Machao Square, people had hung up swathes of brightly-colored fabrics and balloons alongside messages asking: “Who ordered Marielle’s murder?”

“Our day-to-day existence is about activism. It comes from pain, from longing,” said Marcelo Freixo, a state legislator and friend of Franco who was among the mourners.

“We feel embraced by events like these because it shows that our work wasn’t in vain,” said Franco’s sister, Anielle Barboza.

Other tributes included a mass held in the center of Rio and a walk following Franco’s final path on the day she lost her life.

Although the murder of Franco and her driver sent shockwaves through Brazil, the police investigation appears to have stalled.

Public Security Minister Raul Jungmann confirmed that the bullets used were police issue, but he claimed they had been stolen from the force “years ago” in an area more than 2,000 kilometers (1,200 miles) away.

As the one-month anniversary of her killing loomed, Amnesty International urged the government to solve the crime.

“Brazilian authorities must prioritize solving the killing of human rights defender Marielle Franco and her driver, Anderson Gomes, and bring all those responsible to justice,” it said.

No-one has been arrested for the murder of Brazilian politician and activist Marielle Franco and the police investigation appears to have stalled

“Society needs to know who killed Marielle and why. Every day that this case remains unsolved the level of risk and uncertainty surrounding human rights defenders grows worse,” said Jurema Werneck, executive director at Amnesty International Brazil.

As a black woman from the Mare favela, one of the city’s most violent areas, Franco stunned many when she was elected to a city council seat in 2016.

She won fame as a rights activist, particularly for highlighting police brutality in the impoverished, sometimes lawless favela districts.