A controversial group on Sunday clashed with demonstrators in Paris opposed to France's plan to legalize gay marriage.

The Socialist government of Francois Hollande earlier this month sent a proposed plan to legalize marriage and adoption for gay couples to lawmakers for debate. The National Assembly is expected to start examining the legislation in January, and a vote could come by mid-2013.

Female members of the Ukranian group Femen – topless and chanting “in gay we trust” – turned up at the Catholic group Civitas' march protesting the marriage reform.

Femen activists' counter-protest included spraying demonstrators with white powder from bottles. Some media described the substance as “powdered sperm.”

The incident, which escalated into violence leading to 5 arrests, came a day after tens of thousands of demonstrators took to the streets of Paris, Lyon, Marseille and other major towns and cities in protests supported by the Roman Catholic Church. Police estimated 70,000 people took part in the Paris demonstration. Organizers put the figure at 200,000.

(Related: Pope Benedict XVI calls on the French Church to fight gay marriage.)