Brazil's President Jair Bolsonaro on Monday warned of a possible exodus from Argentina after the country's center-right leader Mauricio Macri suffered a major defeat in weekend party primaries.

Populist center-left candidate Alberto Fernandez's crushing victory over the pro-business Macri ahead of Argentina's general election in October sent the country's peso and stock market plunging.

"We don't want our Argentine brothers fleeing here," far-right Bolsonaro said, likening Fernandez's running-mate, former president Cristina Kirchner, to Venezuela's socialist President Nicolas Maduro and Cuba's Fidel Castro.

Kirchner, who was president from 2007-2015 after succeeding her husband, has been tainted by corruption scandals but remains popular.

Bolsonaro said her return to power could put Argentina "on the same path as Venezuela," where a deepening political and economic crisis has forced millions to flee.

"If the leftists return to Argentina, we could have a new Roraima," Bolsonaro said, referring to Brazil's northern state where thousands of Venezuelans have crossed into the country.