Thousands of people took to the streets of Lisbon on Sunday to protest a call for the far-right anti-immigration Chega party to be banned.

"Shame", "We will resist to the end" and "For freedom of expression, against corruption" were among slogans written on placards at the march.

"I'm here for all the Portuguese who weren't brave enough to come but share the same indignation," taxi driver Joao Silva told AFP.

A heavy security presence flanked the march, which drew protesters from across the country, responding to a call by Chega (Enough).

Former presidential candidate Ana Gomes, a socialist, is leading the call for a Chega ban, going to court in February. There are also calls for a probe into the party's finances.

The anti-corruption activist accuses Chega of harbouring xenophobic ideas in violation of Portugal's constitution.

"We are here to show that we are afraid of no-one," party leader Andre Ventura said at the demonstration, adding that "only the people can ban the party, and no-one else."

The demonstrators chanted Ventura's name as security forces struggled to enforce social distancing guidelines against the spread of COVID-19.

Chega entered parliament for the first time after last year's legislative elections, winning 1.3% of the popular vote.

Ventura, an ally of France's Marine Le Pen and Italy's Matteo Salvini, has floated the idea of a special anti-Covid quarantine for Portugal's minority Roma.

Ventura captured almost 12% of the vote in a presidential election in January, just behind Gomes, who won about 13%.

"It's incredible to try to ban a party that won half a million votes," a Chega activist said at the demo. "It's as if voters aren't important," she said, requesting anonymity.

A counter-demonstration opposing the far-right drew several dozen people in another district of Lisbon.