Former President Cristina Fernandez de Kirchner said she will run for the Argentine senate, reviving her political career and setting the stage for a messier dispute for control of the congress in South America's second largest economy.

In December, she was charged over corruption allegations as a federal judge ordered the freezing of $US633 million ($837 million) of her assets. She ran the country for eight years; Argentine presidents make an annual salary of $US131,000.

The former president, who ruled the the country between 2007 and 2015, will pit herself against former allies Florencio Randazzo and Sergio Massa who lead separate factions within the Peronist movement. Congressional elections will take place on Oct. 22.

A win by Fernandez de Kirchner has the potential to scare away investors who are already wary of how the reforms implemented by President Mauricio Macri could be reversed if he loses support in congress.

Macri has succeeded in reopening parts of Argentina's economy. But investors are still skeptical about a country that has defaulted seven times in 200 years and experiences an economic crisis about once a decade. Just this week, MSCI decided against raising Argentina to emerging market status because it wasn't convinced the changes were irreversible, costing the nation billions in new investment.

Roll of dice

"If she returns then uncertainty will skyrocket," Jimena Blanco, head of Latin America research at Verisk Maplecroft, said by phone from London ahead of Fernandez's announcement.

For Fernandez, 64, the move is a final roll of the dice; if she didn't run it would have spelled the end of her political career. Her candidacy will mean a more polarized election, with the government using her to contrast itself with her protectionist policies. Fernandez is seen as favouring the return of currency controls and subsidies that could drive up the country's
deficit.

Still, her chances of winning remain limited, according to Blanco at Verisk Maplecroft. "I don't see how with three separate Peronist tickets she can come first," she said.

Accompanying Fernandez on the senate ticket for the Unidad Ciudadana party is Jorge Taiana, who served as foreign minister during Fernandez's first term in office. Among their aims is putting a brake on Macri's policies, Taiana told Radio Diez on Sunday.

Daniel Scioli, who Macri defeated to clinch the 2015 presidential election, was fifth on Unidad Ciudadana's list of 20 candidates to become deputies for Buenos Aires province, the party said on Twitter.