Dozens of armed security personnel, some with riot shields, were on hand following previous unruly spectator behaviour in Rio, including a brawl between Argentine and Brazilian supporters at the tennis venue.

Team captains Marcelinho Huertas of Brazil and Luis Scola of Argentina met at half court before tip-off to take the microphone in a joint plea for civility.

"We are South American brothers, and we ask everybody to support us in the spirt of the Olympics and in a civil manner," Huertas said to cheers.

Decades of football rivalry spice any Argentine-Brazil matchup, but no incidents were immediately reported.

Argentina dealt a blow to Brazil's hopes of advancing, with forward Andres Nocioni scoring 37 points and guard Facundo Campazzo getting 13 of his 33 in extra time.

Nocioni sank a three-pointer with four seconds in regulation to stun the deafening, mostly Brazilian, crowd and force overtime at 85-85.

Brazil led by as much as six points in the first extra period but Campazzo's slashing moves to the hoop brought Argentina back against a tiring Brazilian defence.

His fast-break lay-up with 36 seconds left in the first overtime tied it at 95-95 and triggered the second extension.

Basketball party                  
                  
Argentina went up by as much as eight and held on to ensure a quarter-finals berth by going to 3-1.

"Unbelievable. The basketball today was just ridiculous," said 39-year-old Manu Ginobili, a four-time NBA champ with the San Antonio Spurs. 

"The heart of some of our players is incredible."

Centre Nene Hilario had 24 points for Brazil, who face winless Nigeria on Monday in their final group game.

Brazil guard Leandro Barbosa rued his team's inability to close out the game.

"We know that we have to keep our heads up and depend on other teams to lose a couple of games," he said.

"That is going to be tough but we still believe that we can qualify for the second round."

Argentina jumped out to an early 11-point lead on 21 first-half points by Nocioni, but Brazil stormed back on the fast break with a 16-2 spurt to end the half in front 52-44.

But Argentina, led by four veterans from their 2004 Athens gold-medal winning side in Nocioni, Brooklyn Nets forward Scola, and guards Ginobili and Carlos Delfino, refused to buckle.

"We were expecting the atmosphere to be as hard as it was," Delfino said of the captains' attempt to rein in passions.

"Both teams talked about it before the game to do it. There is a rivalry between us but ... it's not a war or anything like that."

Said Scola: "We all need to scream, jump, celebrate, cry if they want to, whatever they want to do. But in a civilised matter that we respect."

"We want to have a big basketball party, and it was."

Taunting Argentines has become a theme of the Games with Brazil fans poking fun at the legendary Diego Maradona as Argentina crashed out in men's football earlier.

"Pele scored more than 1,000 goals... Maradona just snorted cocaine," rang around the Olympic stadium as Argentina played Algeria.

Brazil entered Saturday's game desperate for a win to ensure they advance.

Their only victory came at the last-second over Spain, a game marked by ugly taunting of Spanish NBA star centre Pau Gasol.