Thousands took to the streets of Brazil’s largest cities on Thursday night to protest the execution-style murder of a popular Rio de Janeiro city councilwoman. 

Marielle Franco, 38, a rising star in the Socialism and Liberty Party (PSOL), was shot dead in her car on Rio’s north side, by two unidentified assailants around 9.30pm on Wednesday night. 

Tributes have been flooding in on social media with celebrities like supermodel Naomi Campbell honouring Ms Franco’s life and work. 

Ms Franco had been tirelessly campaigning for LGBT, women’s and human rights in the city, and had been particularly vocal in her criticism of alleged police killings of poor residents.

Investigators, prosecutors and even drug gang leaders in Rio de Janeiro has called the murder of Ms Franco  – the only black woman on Rio city council – a political assassination.

Tribute: Thousands took to the streets on Thursday night to protest the assassination of Brazilian councilwoman and activist Marielle Franco in front of Rio's Municipal Chamber, downtown Rio de Janeiro, Brazil

Rest in peace: Friends and relatives grieve at the coffin during Ms Francos funeral on Thursday 

Her driver, Anderson Gomes, was also killed, while her press secretary, who was sat in the back seat, suffered minor injuries but was not shot.

Just weeks ago, the federal government decreed that Brazil’s army would take over all security operations through the end of the year in Rio, where murders have risen sharply. 

Franco, part of a commission to oversee the military intervention, harshly criticized the move on Sunday, saying it could worsen police violence against residents.

‘It is far too soon to say, but we are obviously looking at this as a murder in response to her political work, that is a main theory,’ said a Rio de Janeiro public prosecutor, who spoke on condition that he not be named as he was not authorized to discuss the case.

Rivaldo Barbosa, head of Rio’s Civil Police, told reporters, ‘One of the possibilities in analysis is, yes, an execution.’ He did not speculate on who may have been responsible.

Protest: Demonstrators  hold a banner reading 'Marielle lives' during the rally in Rio de Janeiro on Thursday night

United: Young activists lead the way during the march demanding justice for Ms Franco and Mr Gomes

An aerial view from the demonstration in downtown Rio de Janeiro show the huge crowds gathered to protest 

In honour: Protesters carry banners with the names of Marielle Franco and her driver Anderson Gomes  during a protest against their murders in Rio

Campaign: People call for an end to military intervention and police violence in Rio de Janeiro during the protest

An investigator with the city’s police force went further, saying the prime motive appeared to be Franco’s calling out police for allegedly killing innocents in their constant battles with drug gangs.

Political violence is common in Brazil – but typically in smaller or more impoverished cities.

In the months before the 2016 city council elections in Baixada Fluminense, a hardscrabble region the size of Denmark that surrounds Rio, at least 13 politicians or candidates were murdered before ballots were cast.

As night fell on Thursday, crowds gathered in Rio, Sao Paulo and several other cities, with protesters holding aloft banners calling for justice and an end to Brazil’s endemic violence.

‘The path of her own fight is what gives us the strength to carry on,’ said Danielle Ramos, 26, who was attending a rally in Rio de Janeiro in front of the city council building, along with thousands of others.

‘The best way to honor Marielle is to dedicate every second of our days to the fight that she was a part of,’ said Ramos, part of the Olga Benario Womens’ Movement, which battles against violence.

Franco, who was raised in the Mare complex of slums, long one of Rio’s more dangerous areas, received over 46,500 votes in the 2016 election. That total was bested by only four of 51 council members.

On Sunday on her Facebook page, Franco decried what she alleged to be the police killing of two boys during a police raid in an area called Acari.

‘We must scream out so that all know what is happening in Acari right now. Rio’s police are terrorizing and violating those who live in Acari,’ Franco wrote. 

Tribute: Supermodel Naomi Campbell was one of many who took to sopcial media to honour Marielle Franco after her death

Two mourner's hug during Ms Franco's funeral outside Rio de Janeiro's Municipal Chamber in Brazil on Thursday

Cross-country anger: An elderly man lights a candle during a rally against the murder of Ms Franco, in Sao Paulo, Brazil

Investigation: Police officers work on a crime scene as they stand next to the car where Ms Franco and her driver were shot dead by two unidentified attackers in Rio de Janeiro, Brazil

‘This week two youth were killed and tossed into a ditch. Today, the police were in the street threatening those who live there. This has been going on forever and will only be worse with a military intervention.’

Calls to the police unit assigned to the Acari area were not returned. In a Sunday statement to the O Dia newspaper, police said they carried out an operation in the area, were fired upon by drug traffickers and returned fire, but had no knowledge of any deaths.

Mare’s roughly 130,000 residents must contend with the presence of Rio’s two most powerful gangs, the Red Command and the Pure Third Command. There are also militias often made up of off-duty or retired police and firefighters who are as feared as the gangs.

High-level members of both the Red Command and the Pure Third Command told Reuters their gangs had nothing to do with the killings. It was impossible to reach any militia members.

Raul Jungmann, who heads the federal government’s newly created Public Security Ministry, said at an event in Sao Paulo that Franco’s killing was ‘another lamentable, daily tragedy that takes place in Rio de Janeiro.’

‘We must understand extremely well the reasons behind this and go after those responsible,’ he said. ‘But this does not put at risk the federal intervention.’

Jungmann said federal investigators would be involved in the investigation and that he had put Brazil’s federal police at the disposal of local investigators.

Hundreds of mourners gathered outside Rio’s city council building, where Franco’s body briefly lay in state, while vigils and protests were planned in at least six other cities in Brazil. About 150 members of the PSOL party on Thursday entered Brazil’s federal Congress carrying flowers and signs demanding justice.

The United Nations office in Brazil and Amnesty International demanded a quick, transparent investigation into Franco’s killing.