Protests have lasted for three days outside the Carrefour Brasil supermarket in the southern Brazilian city of Porto Alegre after the security guards beat to death a Black man at the store.

Rio de Janeiro protesters carried banners reading "Murderous Carrefour" and "Black Lives Matter," using the slogan prominent in the United States during demonstrations against police brutality that led to the killing of minorities.

A video taken Thursday night in the southern city showed 40-year-old welder Joao Alberto Silveira Freitas repeatedly being punched in the face and head by a security guard while he is being restrained by another at a Carrefour store.

The clip quickly went viral on social media, and triggered a first round of demonstrations on Friday. In Sao Paulo, dozens of protesters smashed the front windows of a Carrefour store with rocks, pulled off the front doors and stormed the building, spilling products into the aisles before dispersing. In Rio de Janeiro, roughly 200 shouting protesters gathered outside of another Carrefour store.

More protests were held on Saturday, when Silveira Freitas was buried.

In Rio de Janeiro on Sunday, around 100 protesters gathered at a shopping center where one of the French chain supermarkets is located, AFP journalists reported.

Other protests brought drew several dozen people demanding a boycott of Carrefour in various parts of the country, such as Salvador de Bahia or Santos.

In a series of tweets in Portuguese on Friday, Carrefour CEO Alexandre Bompard expressed his condolences over the "horrible act" and said that the images were "unbearable."

He also ordered "a complete review of training for employees and outsourced personnel in matters of safety, respect for diversity" and "rejection of intolerance."

Djefferson Amadeus of the Institute for the Defense of Black People, who was demonstrating on Sunday in Rio, however said "we no longer accept those apologies. They have promised us measures, but so far we have not seen anything."

Other protesters echoed his concerns about structural racism in Brazil, a country where around 55 percent of its population of 212 million identifies as black or mixed-race.

The incident happened the night before the country marked Black Consciousness Day. Brazilians like to think of their country as a harmonious "racial democracy." But the influence of slavery, abolished in 1888, is still evident.

Black Brazilians are almost three times as likely to be victims of homicide, according to 2019 government data.

"We are not going to shut up while they continue to kill our people," said Thais dos Santos, 23.

"This shows that racism is still very present in Brazil, not only in the supermarket, but also in the favelas," he added, referring to Rio's poor districts.

(With input from agencies)