"On the orders of President Kais Saied, Tunisian authorities ordered the departure of Esther Lynch," head of the European Trade Union Confederation, the presidency said in a statement.

Lynch "took part in a demonstration organised by the (UGTT trade union federation) and made comments that constituted blatant interference in Tunisia's internal affairs," it said.

It added that she had 24 hours to leave the country, where she was considered "persona non grata".

Earlier in the day, Lynch had given a speech to thousands of people at a demonstration organised by the UGTT in Tunisia's second city Sfax, one of several protests around the country over the faltering economy and the arrest of a top trade union official.

Speaking through an interpreter, Lynch said she had come to deliver a message of "solidarity from 45 million workers around Europe".

"We say to governments: hands off our trade unions, free our leaders," she said.

The government must "sit down and negotiate with the UGTT for a solution" to Tunisia's woes, she added.

The demonstrations were partly organised to demand the release of senior UGTT official Anis Kaabi, who was arrested on January 31 following a strike by toll booth staff.

The union has described his arrest as "a blow to union work and a violation of union rights".

It came a year and a half after Saied sacked the government.

Since his move, he has been repeatedly accused of dragging the country back into authoritarianism.

Kaabi faces trial from February 23 on charges of "using his position to harm public authorities".

Othmane Jallouli, the UGTT's deputy chief, told demonstrators that "today, any union member can be sacked simply for expressing an opinion".

The protests also came as Tunisia is in drawn-out talks with the International Monetary Fund for a bailout loan, which the UGTT has warned is likely to entail painful austerity measures.

Demonstrators in Sfax, where the largest protest took place, chanted "Tunisia is not for sale!" and "no to removing subsidies!"

Some raised loaves of bread in a symbol of protest at soaring living costs.

Jallouli said "the government has failed to put the country on the path of economic and social reforms. All it has succeeded in is attacking the union".