At least 49 policemen have been injured in clashes with demonstrators protesting against the reopening of a rubbish dump on Tunisia's tourist island of Djerba, an interior ministry spokesman has said.

"A large number of protesters in the centre of Guellala attacked a police post with rocks and petrol bombs," Khaled Tarrouche said on Saturday.

"There were 49 police injured, with fractures and other injuries caused by rocks and petrol bombs."

He said six police vehicles were burned and that no arrests were made.

Tarrouche said reinforcements have been sent from the capital to Guellala, a town of some 13,000 people in southern Djerba, a popular tourist destination.

Calm had returned by early evening after the crowd dispersed following use of tear gas by the police.

At least two protesters have also been injured in the clashes that erupted when police tried to clear demonstrators blocking the entrance to the reopened garbage dump.

Since last year's revolution that ousted former dictator Zine El Abidine Ben Ali, the southern holiday island has been spared the kind of violence afflicting other parts of Tunisia where clashes between police and protesters are common.

On Friday in the central town of Sidi Bouzid, police fired rubber bullets and tear gas to disperse hundreds of protesters who tried to break into the regional government headquarters.

Such protests have multiplied in recent weeks, amid rising discontent over poor living conditions, including unemployment, regular water cuts and the state's failure to collect rubbish, as well as other social grievances.