Some 75,000 people, according to police estimates, joined anti-crime crusader and march organiser Juan Carlos Blumberg, whose son was killed in March in a botched kidnapping. He also led the first two protests in April.
"Four months have passed. Gentlemen, get moving. Listen to the citizens," Blumberg said in his speech, expressing disappointment with government and lawmakers' efforts to reduce crime.
On April 1, Blumberg led 135,000 people through Buenos Aires, surprising the government and making him a hero among a middle class worn down by spiralling violence after the economy's collapse in 2001 and 2002.