In the most serious attack, a mob stormed a police station at Menzel Bourguiba, 65 kilometres (40 miles) north of the capital, early Sunday, making off with weapons.
Four of the six officers hurt in that incident were in intensive care in Tunis, said a ministry statement, denouncing "the work of certain extremist forces to destabilise order and sabotage the electoral process."
In other incidents, crowds attacked police stations in Kairouan, central Tunisia; in Sousse, 150 kilometres south of Tunis; Hammam Ghzez in the east of the country; Al Agba, west of the capital; and in a working class district of Tunis, the statement added.
Public buildings and shops were also damaged.
In the Intikala district of Tunis, up to 400 people, some throwing stones and Molotov cocktails, tried to storm the main police station overnight in clashes that lasted several hours, witnesses told AFP.
On Sunday, burnt tyres, stones and the remains of barricades were littering the street outside the station. Inside, traces of molotov cocktails and broken windows bore witness to the night's events.
"They came with the deliberate intention of burning down the station," a police officer, who asked not to be named, told AFP.
"Some of them had sabres, others threw molotov cocktails. It was well organised," he added.
Feelings have been running high in Tunis since Friday, when police violently dispersed a few hundred people who tried to stage a sit-in outside central government buildings.