The fight occurred in a McDonald's restaurant in the Lezama park area, about one kilometre away from the La Bombonera stadium in Buenos Aires.

"One man who is about 55 years old has a serious craneoencephalic trauma, is in a coma and his health condition is critical," Alberto Crescenti, director of the federal emergency services SAME, told cable news channel C5N.

"The woman is 85 and her name is Delia Campos. She had a bullet in one leg but it went into it and went out."

Both were admitted to the Cosme Argerich hospital in the capital.

Six people have been detained and one gun has been found according to local reports.