Metalworker Paula Gonçalves, 51, said people were "protesting against low wages, precariousness and for more justice" for workers.
"We, the workers, are the ones who produce, we give everything we have... and the profit is all for employers and nothing for us," she said.
Portugal is one of Western Europe's poorest countries and official data shows that more than 50% of Portuguese workers earned less than 1,000 euros ($1,067) per month last year, while the minimum wage is only 760 euros per month.
According to Eurostat data, the minimum wage in Portugal - measured in purchasing power parities and not at current prices - in 2023 is 681 euros a month, the 12th lowest of the 15 European Union countries that have minimum wages. It compares with 726 euros in Poland, 775 euros in Greece or 798 euros in Spain.
Portugal's biggest umbrella union, the CGTP, which called the protests, is calling for wages and pensions to be raised by at least 10% immediately and wants the government to impose caps on the price of basic foods.
Portugal's economy minister Antonio Costa Silva ruled out on Friday any government intervention to stem soaring food prices, seeing the market as the best price-setting mechanism.
As of Jan. 1, civil servants' salaries were up by an average of 3.6% from 2022 levels and those of the private sector grew by 5.1%, while pensions rose by a maximum of 4.83%, government data shows.
Portuguese inflation slowed to 8.2% in February from 8.4% the previous month. Prices of unprocessed food products, such as fruit and vegetables, surged 20.11%.
A year after Socialist Prime Minister Antonio Costa won a majority in parliament, he is facing street protests and strikes by teachers, doctors, railway workers, and other professionals.
"Each time I go to the supermarket I see that the (prices of) products increase a little more every day and wages do not follow... it is urgent to cap the increase in the cost of living," said Ana Amaral, 51, a hospital administrative assistant.
($1 = 0.9376 euros)
(Reporting by Sergio Goncalves and Miguel Pereira; Editing by Emelia Sithole-Matarise)
By Sergio Goncalves and Miguel Pereira