Police in Tunisia shot dead four people in the northwestern town of El Kef when they opened fire at a group of protesters.
Officers fired at a crowd of several hundred people after they threw stones and fire bombs at a police station.
Two men died at the scene and 17 people were wounded.
Two of those later died of their injuries.
The crowd had gathered outside the station in El Kef to call for the resignation of the local police chief.
There are allegations that one senior officer based there assaulted a local woman.
On Saturday, two members of the Tunisian security forces were arrested in Sidi Bouzid over the death of two detainees earlier last week.