Brazilian activists have taken to the streets in five major cities after the death of a young black man who was restrained by a supermarket security guard.

Campaigners said the protests are feeding a nascent Black Lives Matter movement in Brazil, where nearly three-quarters of all homicide victims are black.

Outside the Extra supermarket in the upscale Barra da Tijuca neighbourhood of Rio de Janeiro, demonstrators chanted the name of Pedro Gonzaga, who died of a heart attack in hospital on Thursday after being immobilised with a “sleep hold” by a security guard. Protests were also reported in São Paulo, Belo Horizonte and Fortaleza. Another took place on Saturday in Recife.

Lyz Ramos, 19, a student painting placards in Rio, said: “We have to take a position against this to stay alive. It’s a basic issue.”

Protesters outside the Extra supermarket in Rio where Pedro Gonzaga, 19, was immobilised with a ‘sleep hold’. Photograph: Dom Phillips/The Guardian

Gonzaga, 19, was immobilised by Davi Amâncio. Video footage showing the prone Gonzaga underneath Amâncio while onlookers pleaded for him to be let go generated widespread anger. One woman can be heard saying: “He is suffocating him.” He was taken unconscious to hospital, where he died.

As the outcry grew, the hashtag #VidasNegrasImportam (Black Lives Matter) began circulating, and black Brazilians compared his death to that of Eric Garner, who died after police in New York immobilised him in 2014.

Rene Silva, one of the organisers of the Rio protest and the founder of the Voz das Comunidades, a newspaper from Rio’s Complexo do Alemão favela complex, said: “There has never been a Black Lives Matter [movement] in Brazil to compare to the United States, but this year I think it will happen more often because the black community is more and more united.”

Silva said the protest was for all the black people being killed, citing the case of Jenifer Gomes, 11, who died last week in Rio. Residents blamed the city’s police – recently accused of executing 13 unarmed men in a Rio favela, including drug gang members – but officers have denied responsibility.

“We want to talk about more about black lives matter, for society to understand we can’t stand racism anymore,” he said.

Black activists, rappers and celebrities shared details of the protests and expressed revulsion over Gonzaga’s killing. Lucy Ramos, an actor, shared a lyric from the singer Elza Soares: ”The cheapest meat in the supermarket is black meat.”

Augusto Trota, 19, a car cleaner and friend of the victim, said Gonzaga had hoped to become a successful rapper performing funk, a Rio style of hip-hop. “He was a good person, you could count on him at any time,” Trota said.

O Globo newspaper reported that Gonzaga was a drug user and was being taken by his mother, Dinalva Oliveira, to a rehabilitation clinic when they stopped at the supermarket’s food court to have lunch, and he had a fit or hallucination.

André Barreto, a lawyer for Groupe Protection, the security company at the store, told the Folha de S.Paulo newspaper that Gonzaga ran towards the security guard, threw himself on the ground and simulated a fit. The security guard put him on his side and raised up his head, but Gonzaga seized his weapon and began threatening people, Barreto said. Another security guard took the weapon, Gonzaga attacked Amâncio again, and the two began a struggle, he added.

Video being shared on social media from television news reports showed Gonzaga approaching the security guard, who was standing beside a supermarket staff member, falling to the ground, getting up and falling to the ground again.

The YouTuber Felipe Neto tweeted: “Security camera video proves there was no attempt to take the security guard’s weapon.”

According to the government-produced 2018 annual Violence Atlas, 71.5% of the 64,000 people killed each year in Brazil are black or mixed race. Black or mixed race people make up just over half of the Brazilian population.

Vanderlea Aguiar, 42, a public servant taking part in the protest, said it was nearly a year since Marielle Franco, a black city councillor, was killed, yet nobody had been charged with her murder. “Every day we get more news of more youth dying,” she said. “A big movement is growing every day and we are making more people aware.”