Tunisia's alternative law enforcers
30 July 2013 Last updated at 12:07 BST
For years, the Arab world's dictators kept radical Islamic groups in check, but the uprisings of 2011 gave them freedom to operate more openly.
In Tunisia, where the Arab Spring began, a tiny but well-organised minority of fundamentalists, some of them violent, have been imposing their morality on others.
Nowhere is this more visible than in the small town of Bizerte, a coastal city that lies 60 kilometres north of Tunis on the Mediterranean Sea.
There Salafists have even formed groups who patrol the streets intervening whenever they see behaviour which they say does not meet the requirements of Sharia law.
Some locals support the Salafists, saying that during the days of disorder which followed the Arab Spring, when the police were absent, it was they who protected people and prevented looting, others see them as a dangerous challenge to the state, as Tim Whewell reports for Newsnight.
You can see BBC Arabic's film, The Battle for Bizerte, on BBC World on Saturday 17 August.