Argentine legislator Héctor Olivares died three days after being seriously wounded in a gun attack that killed a provincial official, a Senate official said Sunday.

Acting Senate president Federico Pinedo said Olivares died of his wounds earlier in the day.

"A great pain the death of Deputy Olivares," Pinedo tweeted.

ARGENTINE LAWMAKER FIGHTING FOR HIS LIFE AFTER BEING AMBUSHED BY GUNMEN

President Mauricio Macri decreed a 48-hour period of national mourning.

At least six people have been detained in what has been described as a "mafia-style" attack Thursday that shocked Argentines. Officials have said two gunmen in a parked car shot wounded Olivares and killed Miguel Marcelo Yadón near the country's congressional building in Buenos Aires.

Olivares, a member of the pro-government Radical Civic Union party, represented La Rioja province in the Chamber of Deputies, the lower house of congress. Yadón worked for La Rioja's federal electric transportation system.

Authorities have said investigators are working to determine a motive.