A Salafist is one of the main suspects involved in the killing, Interior Minister Lotfi Ben Jeddou said.
Gunmen on a motorbike shot Mr Brahmi, who led the Movement of the People party, in his car on Thursday morning.
The governing Islamist Ennahda party has rejected accusations from relatives that it was complicit in the killing.
In February, the murder of prominent secular figure Chokri Belaid sparked mass protests and forced then-Prime Minister Hamadi Jebali to resign. http://www.bbc.co.uk/news/world-africa-23465849 -- Wojtek
"An anarchist is a neoliberal without money."