By Elliott Gotkine BBC correspondent in Buenos Aires

Protesters say action on crime is long overdue

The peaceful protest was convened by the parents of 23-year old Axel Blumberg, who was kidnapped and murdered a week-and-a-half ago.

Demonstrators called for harsher penalties, particularly for gun-related offences and kidnappings.

In response, Argentina's Congress has convened an extraordinary session for next Wednesday, to discuss the demands.

The Argentine capital is no stranger to demonstrations.

But not since the country's economic meltdown, a little over two years ago, has so many people taken to the city's streets.

Waving placards bearing pictures of murder victims and holding candles to show their solidarity with the Blumberg family, the massive crowd held a minute's silence before being addressed by Axel's father.

In an emotional speech, a tearful Juan Carlos Blumberg called on the government to imprison people caught carrying unlicensed guns, and to impose stiffer penalties on kidnappers.

"We're not going to ask," he said, "we're going to demand a change in the laws."

Corrupt police

The people who gathered in front of Argentina's Congress to listen to him, agreed that action on violent crime was long overdue.

"I go to work in the morning and I don't know if I'm going to come back in the evening," said one protester. "I work all day in the street, and it's insecurity, to live in fear that they stop you at a street corner and they take you away."

Another said: "The problem here is not that we have criminals, but we have police officers who are criminals."

Argentina's President, Nestor Kirchner, would appear to agree.

He has already said that many of the kidnappings carried out in and around Buenos Aires were masterminded by corrupt police officers, several of whom have been arrested.

If current trends continue, it is estimated that some 400 people will have been kidnapped by the end of the year.