Argentina's ruling coalition led by President Alberto Fernandez is expected to suffer major losses in midterm elections amid public frustration about the spread of the coronavirus and an economic downturn.
A third of the Senate seats and about half of the seats in the lower Chamber of Deputies were contested in Sunday's elections.
Local media report that the president's center-left coalition has secured about 33 percent of the votes in the lower chamber, with more than 95 percent of the ballots counted.
The center-right opposition coalition has gained about 42 percent of the votes.
In the Senate poll, the opposition bloc is also leading the ruling bloc by nearly 20 percentage points.
Local media say the ruling coalition is likely to lose its majority in both the Senate and the lower chamber.
More than 5 million people have been infected with the coronavirus and over 110,000 have died in the Latin American country despite its quarantine and other measures.
Argentina has an annual inflation rate of more than 50 percent. About 40 percent of the population lives in poverty.