A Spaniard linked to the far-right 1977 slayings of five people in Madrid will be extradited from Brazil this Thursday, his lawyer told AFP.

Spanish prosecutors had been seeking the return of Carlos Garcia Julia since his arrest in December 2018 in Sao Paulo.

Garcia Julia was among a group of gunmen, linked to a far-right organization, who on January 24, 1977, attacked a law firm working for labor unions.

They killed three Communist lawyers, a student and an employee in the attack on Madrid's central Atocha Street. Garcia Julia was among those convicted in 1980 of the murders.

"It's expected he will arrive on Friday in Spain," the lawyer, Daniel Mourad Majzoub said.

For security reasons, no further details will be released, he said.

The "Atocha Massacre" shocked Spain while it was undergoing the transition to democracy and shaken by murders. It led to the legalization of the Communist Party three months later.

In 1991, a judge granted Garcia Julia parole and allowed him to move to Paraguay but he disappeared shortly after.

He is believed to have moved around Latin America before finally settling in Brazil where he was reportedly working as an Uber driver using a fake name.

Garcia Julia, who is in his 60s, still has 10 years to serve on his sentence.