Over 500,000 opponents of same-sex marriage have flooded the streets of Paris and Bordeaux to protest against medically-assisted reproduction for gay couples, rally organizers said. A previous protest for “traditional family values” gathered 100,000.

Streets of Paris and Bordeaux have been smothered in pink, blue and white as scores of demonstrators have been waving flags of the "Manif pour Tous" (Protest for Everyone) group that organized the two rallies.

The group said that “at least 500,000 attended the demonstration” in Paris alone. This is five times higher than the previous rally for “family values” back in February.

In Bordeaux, at least 7,500 people attended the rally, police said. However, organizers estimated that no fewer than 30,000 activists came.

À 15 minutes du départ de la "Manif pour tous" à #Bordeaux, bien loin des 15 000 personnes attendues par la MPT33 pic.twitter.com/xNqQNoGVEb — Aude Courtin (@AudeCourtin) October 5, 2014

Manif pour Tous expected a higher turnout, as a petition calling for a mandatory ban on surrogacy by French citizens had been signed by 200,000 people by Sunday morning, four days after it was put online, according to local Libération newspaper.

Generally opposing same-sex relations, the group’s Sunday march was to protest surrogacy and medically-assisted reproduction (ART) for gay couples.

“Because the exploitation of women is intolerable; because the child is not an object; because all children need a father and a mother,” the group’s announcement said as it called for people to come out and support “traditional family values.”

The group said it has been out on the streets of France “for two years with the same message” and it “continues on October 5.”

The call has been supported by tens of thousands of people in both Paris and Bordeaux, where the rallies started an hour apart – at 1pm and 2pm respectively.

In Paris the demonstrators gathered at Porte Dauphine and marched to Montparnasse, which are about 7km apart.

The president of Manif pour Tous, Ludovine de la Rochere, said that “traditional family values” must be “fought for at all costs.”

According to an exclusive research by Ifop poll for the local Atlantico website, 31 percent of French people support the “values and ideas” of Manif pour Tous.

Speaking to Catholic daily La Croix on Friday, French Prime Minister Manuel Valls assured anti-LGBT supporters that surrogacy "is and will remain banned in France."

In September, the highest French appeals court ruled that lesbian couples in France may adopt children born via assisted reproductive technology (ART).

But while homosexual couples in France are allowed to adopt, they are barred from using in vitro fertilization.

President Francois Hollande signed the controversial marriage bill into law in May last year, making France the 14th country in the world to allow gay marriage.

The legislation was opposed by many people in France, although opinion polls at the time showed that 55-60 percent of French people supported gay marriage.