A Reuters witness said young people aged around 20 were throwing stones at police vehicles and setting fire to tyres.

The clash happened in Ettadamen, a poor district of the capital, Tunis.

President Beji Caid Essebsi had given a speech there earlier on Sunday promising to increase youth employment.

Joblessness among the young is considered a key indicator of a country's economic prospects, and Tunisia's stands at around 35%.

The president's comments came as Tunisians marked the seventh anniversary of the country's revolution. The 2011 uprising that launched the Arab Spring led to the toppling of President Zine al-Abidine Ben Ali after 23 years.

Ben Ali, now in exile in Saudi Arabia, was convicted in absentia of embezzlement and misuse of public funds, and sentenced to 35 years' imprisonment.