By Andrei Khalip

LISBON (Reuters) -A group of neo-Nazis attacked several actors outside a Lisbon theatre late on Tuesday, forcing it to cancel a show about Portugal's national poet Luis de Camoes to mark Portugal Day, which commemorates the literary icon.

The European Union has said hate speech is on the rise in Portugal, and the far-right is gaining support after anti-immigration party Chega became the main opposition in parliament in last month's election.

Culture Minister Margarida Balseiro Lopes condemned on Wednesday what she called a "cowardly attack... on freedom of expression, on the right to creativity, on the democratic values that define us as a country".

Police said they had detained one person after Tuesday evening's scuffle near the Barraca theatre in downtown Lisbon.

Actor Aderito Lopes, who performs the role of the 16th century one-eyed poet in a play titled "Love Is A Flame That Burns Unseen", had to be hospitalised with face injuries.

According to the play's director Maria do Ceu Guerra, the group of about 30 neo-Nazis had been returning from a rally with signs and leaflets that read "Portugal for Portuguese".

They initially verbally assaulted an actress who was wearing a T-shirt picturing a star associated with the political left and then attacked two male actors.

The attack came on the 30th anniversary of the killing of a young Black man, Alcindo Monteiro, in Lisbon by skinheads, similarly after Portugal Day commemorations.

"Thirty years on, this country has not found a way to defend itself from the Nazis," Guerra said in televised remarks.

Under the fascist regime of Antonio Salazar, which ruled the country for four decades until 1974, Portugal Day became known as Portuguese Race Day. Ultra-right movements have been marking it with mainly small-scale rallies for years.

Following Tuesday's attack, left-wing political parties accused Prime Minister Luis Montenegro's centre-right government of failing to take action against far-right groups.

"The neo-fascists are attacking books, the theatre and those involved in culture. They do it because they think they can," Left Bloc lawmaker Mariana Mortagua wrote on X.

In her statement, Culture Minister Balseiro Lopes said: "Culture is not intimidated... And it does not accept hatred disguised as political discourse."

In April, far-right groups provoked clashes in downtown Lisbon, marring celebrations of the 51st anniversary of the Carnation Revolution, which ended the dictatorship.

(Reporting by Andrei Khalip; editing by Charlie Devereux and Gareth Jones)