Police had earlier arrested a Salafi Islamist accused of assaulting the head of Manouba's public security brigade during clashes between alcohol sellers and Salafists in Tunis on Saturday.
The image of an armed brigade blocking access to a public building had so far usually been reserved for Libya's legislature, the BBC's Rana Jawad in Tripoli says.
The London Fire Authority has decided not to challenge Mayor Boris Johnson's order to hold a public consultation on proposed cuts to London Fire Brigade.