Police in Paris made 11 arrests following clashes between groups polarised by Pope Benedict XVI's views over condom use in Africa.
Youths in favour of the Pope fought pro-condom activists staging a protest outside Notre Dame Cathedral as worshippers left after Sunday mass.
Last week the Pope said condoms were not the answer to Aids in Africa, and that sexual behaviour was the issue.
French politicians from a wide range of parties criticised the comments.
The Pope's comments preceded a weekend of demonstrations by Aids activists in France.
Free condoms were distributed outside Notre Dame and Aids-awareness activists Act Up-Paris carried portraits of the pontiff labelling him an "assassin".
The Pope's comments are "deadly", said Eric Marty of Act Up-Paris.
"More than 20 million HIV-positive people live in Africa. Tell people in Africa that condoms make Aids worse, that's not possible, it's an insult for those who suffer from Aids."
But the activists are missing the point, according to Roman Catholic protesters who say the Pope meant that condom use does not provide 100% protection from HIV/Aids.
Two surveys at the weekend showed the German-born pontiff's popularity in France has fallen sharply.