Demonstrators want embattled President Pedro Castillo to resign over allegations of corruption, according to the BBC.
The president, who unexpectedly won power last year, is the subject of six criminal investigations - but denies any wrongdoing.
Peru faces a number of economic issues, including spiraling living costs.
The country was disproportionately badly hit by Covid-19, and poverty levels are forecast to remain above pre-pandemic levels for the next two years, according to the World Bank.
Mr Castillo won the presidency promising to narrow the gap between the rich and the poor, but a Congress dominated by opposition lawmakers has blocked many of his plans.
One of Saturday's protesters told the Reuters news agency she was taking part for the sake of her children and grandchildren, because "this government is becoming hell".
Another told the AFP news agency that the country was "on the edge of the precipice; economically everything has stagnated."
No injuries were reported immediately after police fired tear-gas canisters in Lima in an effort to stop demonstrators from reaching government buildings.
Protests were also reported in a handful of other Peruvian cities, while groups of Mr Castillo's supporters organised a march of their own in a Lima square.
MNA/PR
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