Cristina Fernández de Kirchner, Argentina’s former president and one of the country’s most polarizing political figures, was sentenced to prison on Tuesday and barred for life from public office after the Supreme Court upheld her corruption conviction.

The ruling is likely to deepen political tensions in the country and comes after Mrs. Kirchner, who was the target of an assassination attempt three years ago, announced plans for a political comeback.

Supporters blocked key highways around the capital, Buenos Aires, ahead of the court decision against the left-leaning Mrs. Kirchner, who has clashed repeatedly with Argentina’s right-wing president, Javier Milei, while major labor unions had threatened national strikes.

The Supreme Court rejected an appeal by Mrs. Kirchner, cementing a six-year sentence handed down by a lower court that had found she defrauded the state during her two terms as president, from 2007 to 2015.

Still, Mrs. Kirchner, 72, is unlikely to serve significant prison time as Argentine law often allows house arrest for those over 70. The lower court will determine if Mrs. Kirchner gets home detention.

The former president could be held behind bars at a police station for a few days until a judge approves her home detention, said Andrés Gil Domínguez, a constitutional law professor at the University of Buenos Aires.