Catholics vs Femen: Clashes, tear gas at Paris anti-gay marriage rally. (VIDEO)

Scuffles erupted in Paris on Sunday as a small group of Femen activists tried to disrupt a protest by Catholics against the president's plan to legalize marriage and adoption for same sex couples. What began as a peaceful protest quickly degenerated into violence when some radical members of the Catholic Civitas organization chased the Femen activists off and violently pushed some on the floor, witnesses and journalists on the scene reported. Security stewards opened tear gas canisters to break off the fighting.

A day earlier, throughout France, more than 100,000 demonstrators protested against the president's plan. Femen, a Ukrainian protest group, has gained prominence for staging topless protests against all kinds of political and social problems - from the shortage of hot water to women's rights in the Muslim world to domestic pension reforms.