BRASÍLIA: The death of a black man beaten by white security guards at a supermarket sparked outrage across Brazil Friday as it celebrated Black Consciousness Day.

A video of Thursday night's incident in the southern city of Porto Alegre captured on a witness's mobile phone was broadcast on social networks and Brazilian media. It shows 40-year-old 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 supermarket run by the French group Carrefour.

A woman stands beside them, filming with her mobile phone.

The military police in Rio Grande do Sul state said the man had threatened a female worker at the supermarket, who called security.

Silveira Freitas lost consciousness during the assault and died on the spot as medics tried to revive him.

Both security guards were arrested. One of them was identified as a member of the military police who worked part-time at the supermarket.

In a statement, Carrefour's Brazilian subsidiary deplored the "brutal death" of Silveira Freitas and promised to take "appropriate measures to hold accountable those involved in this criminal case."

Carrefour said it would cut ties with the security company that employed the guards.

The killing sparked outrage on social networks and overshadowed Brazil's Black Consciousness Day, a holiday in several states. "From one November 20 to another, and every day, the racist structure of this country brings us brutality as a rule," social activist Raull Santiago said on Twitter.

"It seems that we have no way out...not even on Black Consciousness day," Brazil international footballer Richarlison said.