The polls had been called after Prime Minister Antonio Costa failed to secure support for his 2022 budget.
Early voting has begun in Portugal for a snap general election, with polls showing the incumbent Socialists still ahead though with their lead over the nearest centre-right rivals narrowing.
Over 300,000 voters have signed up to vote a week early, as polls opened at 8:00 am local (0800 GMT).
The early voting option was provided this year to reduce crowding on election day, next Sunday, due to the pandemic.
"I preferred to vote today as today I'm fine – next Sunday, I don't know," proffered one early voter, Elisa Fialho, a woman in her 70s who turned out to cast her ballot with her husband in the capital Lisbon.
Prime Minister Antonio Costa, who has led two consecutive minority Socialist governments since 2015, also cast his ballot in the northern city of Porto.
"All the conditions are there for everybody to go out and vote in security," said Costa after voting.
Portuguese voters who are infected and in isolation, on the other hand, will be allowed to leave home to cast their ballot next week, with a recommended hour-long slot when polling stations are traditionally less busy.
Officials estimated as many as 600,000 people are currently in quarantine.
The snap polls were called after Costa failed to secure support for his 2022 budget from the two smaller far-left parties that had been propping up his government.
Costa has blasted his former allies – the Left Bloc and the Communist Party – as "irresponsible" for voting down his budget and has appealed for voters to give him an outright majority in parliament.
It was the first time a budget was voted down since the EU member returned to democracy in 1974.
The Socialists have around 38 percent support, compared with just over 30 percent for the main opposition centre-right PSD, according to a poll of polls compiled by private Radio Renascenca.
But surveys carried out in recent days have shown the gap narrowing, with at least one putting the two parties in a statistical tie when the margin of error is taken into account.
The election could see gains for the upstart far-right party Chega, which entered parliament for the first time with a single seat during the last election in 2019.