Shadowy criminal gangs operating in Rio de Janeiro are the chief suspects in last month's murder of Marielle Franco, a prominent black rights activist and city councillor, a government minister has said.
"The most likely hypothesis is that it was done by the Rio de Janeiro militias," Public Security Minister Raul Jungmann told CBN radio.
He was referring to armed groups of current and former police officers who vie with criminal gangs for control of Rio's poor communities and who have been accused of summary executions. The groups often run protection rackets and undertake other ‘mafia-like’ activities.
Without providing further details, Jungmann said investigators were "following one or two strong leads."
Franco was gunned down in central Rio on March 14 in what police say appears to have been a targeted assassination. So far, no arrests have been made. Her driver was also killed.
The 38-year-old was elected to Rio's municipal council in 2016 and made a name for herself as an outspoken activist against racism and police brutality in Rio's sprawling favelas, the poor neighbourhoods where security forces battle heavily armed drug gangs.
Just days before her death, she had accused one police unit of acting as a death squad.
The organised nature of the killing immediately prompted speculation that Franco was murdered by one of the militias.
Last Saturday, a handful of quiet memorials took place in Rio de Janeiro remembering Franco.
At one ceremony in Largo do Machao Square, people had hung up swathes of brightly-coloured 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 centre of Rio and a walk following Franco's final path on the day she lost her life.
Jungmann has 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 kilometres away.
As the one-month anniversary of her killing loomed, Amnesty International urged the government to solve the crime.
"Brazilian authorities must prioritise solving the killing of human rights defender Marielle Franco and her driver, Anderson Gomes, and bring all those responsible to justice," it said.
"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.