Tunisian police have arrested dozens of Islamists for an attempted attack on a TV station which had showed the award-winning film Persepolis.
Officials said the activists had tried to set Nessma TV station alight after it broadcast the animation, which they deem to be blasphemous.
Police clashed with other Islamists who want a ban on women wearing the niqab at university lifted, reports say.
The protests come ahead of elections for a constitutional assembly.
The poll, in two weeks' time, will be the first vote in Tunisia since long-time President Zine al-Abidine Ben Ali was toppled in an uprising in January.
Correspondents say that with the autocratic government of Ben Ali gone, more conservative Muslims are making themselves heard.
The main Islamic party in Tunisia, Ennahda - which is set to do well in the polls - has condemned the demonstration.
'Stones and knives'
Persepolis, which was broadcast on Friday by the channel, is a French-Iranian animation feature based on an autobiographical graphic novel by Marjane Satrapi.
It depicts the last days of the Shah and Iran's 1979 Islamic Revolution.
The protesters are angered by fantasy scenes in which God is shown talking to a young girl.
Interior ministry spokesman Hichem Meddeb told AFP news agency that police stopped the protesters before they could reach the offices of the Nessma private television channel, and arrested around 50 of them.
Mr Meddeb said there were casualties, but did not say how many or give further details.
"Three hundred people attacked our offices and tried to set fire to them," Nessma chairman Nebil Karoui told AFP.
In a separate area of Tunis, police used tear gas against hundreds of Islamist protesters who attacked them with stones, knives and batons, Reuters news agency reports.
Demonstrators gathered outside the main university campus in Tunis, before heading to the neighbourhood of Jebel el-Ahmar, north of the city centre, where clashes broke out.
About 100 police vehicles and several hundred riot police were at the scene, Reuters reports.
Ennahda, a moderate Islamist party, said it condemned the attack on Nessma and described it as an "isolated incident" that should not spark concern.
The party is a front-runner in elections on 23 October.
Correspondents say that the main contest in Tunisia is between those who want to see religion play a greater part in public life, and secularists who think Islam should be confined to mosques.