The North African country is in drawn-out talks with the International Monetary Fund for a bailout loan, which the powerful UGTT workers' federation has warned could entail painful austerity measures.

Demonstrators in Sfax, where the largest protest took place on Saturday, 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.

They also demanded the release of senior UGTT official Anis Kaabi, who was arrested on January 31 following a strike by toll barrier workers, in what the union has described as "a blow to union work and a violation of union rights".

Othmane Jallouli, the UGTT's deputy chief, told demonstrators that "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".

"Today, any union member can be sacked simply for expressing an opinion," Jallouli said.

European Trade Union Confederation head Esther Lynch also addressed the crowd in Sfax, delivering 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.

Lynch said the UGTT represented "workers who are struggling to make ends meet".

Tunisia, heavily indebted and import-dependent, is in the grip of a long-running economic crisis that has worsened since Russia's invasion of Ukraine, with regular shortages of basic goods from sugar to petrol.

UGTT members protested across Tunisia at the same time as the Sfax demonstration, from Tozeur in the south to Bizerte in the north.

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