Tens of thousands of people took to the streets of Argentina, banging pots and pans in protest of economic conditions and the government, dpa reported.
The protests late Thursday in Buenos Aires and several other cities were the worst since demonstrations by agricultural workers in 2008 and come a little more than a year since President Cristina Fernandez de Kirchner was re-elected with 54 per cent of the vote.
The demonstrators carried signs that said, "Down with corrupt officials. Throw them all out," "Justice" and "We want security," as well as Argentine flags.
Crowds converged from different parts of the capital and suburbs on the obelisk in the Avenida 9 de Julio, a traditional gathering point for demonstrations.
There was also a mass demonstration outside the tightly guarded presidential residence in Olivos, a northern suburb, and in the cities of Rosario, Cordoba, Mendoza, San Miguel de Tucuman and Salta.
Protesters complained about inflation and Argentina's economic slowdown. They also spoke out against widespread corruption and tight controls on currency exchanges.
The crowds also voiced objections to a proposed reform of the constitution to allow Fernandez de Kirchner to run for a third-consecutive term.
"Yes to democracy, no to re-election," one sign read.
Most protesters appeared to be from the country's sizeable middle classes and included men and women of all ages as well as entire families, many banging pots and pans.
The marches were organized over social networks without any apparent political affiliation. Only a few opposition leaders joined the protests.
The president said on her Facebook page, "We are experiencing a moment of freedom of expression never before seen in Argentina."
"If there is a sector with specific demands, they should stand up and say so clearly," she said, "but please, let no one think that I would go against my own political position, which I have fought for since I was 16."
Officials and lawmakers of the president's Front for Victory party condemned the demonstrations more strongly.
Senator and former cabinet chief Anibal Fernandez said they were "a creation of a right-wing faction" and were paid for by several groups "linked to the most rancid elements of the extreme right," including "remnants of the [1976] military coup."
"I am not with the supporters of the coup or the oligarchs," one Buenos Aires demonstrator's sign read.
"This is the Argentina we do not want, an Argentina of arrogance," one protester said.
Another added, "We just want to express ourselves and for them to listen to us. The insecurity, the inflation, this cannot go on."
Demonstrations were also held by Argentine expatriates in Sydney, Vienna, Geneva, Berlin, Rome, Milan, Paris, Barcelona, Madrid and London.