Blazing barricades, looted shops, scorched cars, hundreds injured - such scenes, which were seen during the G20 summit in Hamburg in 2017, are something this year's host Argentina desperately wants to avoid.
The meeting comes at a time when President Mauricio Macri, whose government had to accept a 56-billion-dollar rescue package from the International Monetary Fund (IMF) earlier this year, is struggling to maintain the goodwill of creditors and rekindle investor interest.
An impression that the government is unable to prevent violent protests would undermine such efforts, and Argentina is deploying 22,000 police and 3,000 soldiers during the two-day summit which begins on Friday.
They will be equipped with 15 million rubber bullets and 2 million rounds of live ammunition, according to media reports.
Awacs aircraft and about 400 US military personnel have meanwhile been stationed in neighbouring Uruguay to provide security for the summit.
"We are on maximum alert," summit coordinator Hernan Lombardi said.
Dozens of groups have announced protests against Macri's alliance with the IMF and the G20 itself, with the biggest demonstration planned for Friday evening.
"We hope for a massive participation," Beverly Keene from the protest alliance Dialogo 2000 told dpa.
Demonstrators are also expected to arrive from Chile and Brazil to join marches called by Argentina's highly organized and combative protest movement.
The authorities will cordon off six security zones which demonstrators are not allowed to enter.
The government is concerned about recent incidents, including a man interfering with the communications system of Buenos Aires' Jorge Newbery airport, as well as a bombing and an attempted bombing attributed to anarchists.
A bus carrying Boca Juniors footballers was also attacked by fans of the opposing team en route to a Buenos Aires stadium, leading to several players being injured.
Germany has been advising Argentina on the security arrangements, and sees Buenos Aires as being well prepared, Hamburg security official Andy Groote told dpa.
The government has made Friday a public holiday and advised residents to leave the city.
