Violent clashes have continued in the Tunisian town of Siliana, where a police crackdown on protests has left hundreds of people wounded this week, as political instability in the north African country mounts. Policemen, backed by armoured cars, fired warning shots and tear gas at hundreds of protesters on Friday evening. The demonstrators hurled rocks and petrol bombs at the security forces, erecting barricades in the town centre and setting some structures on fire. Al Jazeera's Hashem Ahelbarra reports from Siliana in Tunisia.