Police shot tear gas into the crowds to keep protesters from marching on the Champs Elysees, which partly borders on the presidential Elysee Palace.

Paris police had turned down a request to allow a march on the road on the grounds that it was a threat to public order.

Some 300,000 people were present at the protest, according to police, although organizers put the number at 1.4 million. Demonstrators lined a 5-kilometer (3.1-mile) route from the city business district of La Defense to the Arc de Triomphe.

Some protesters bitterly oppose the concept while others say it should not be a priority of the government. Banners on balconies read: "We want work, not gay marriage" and "No to gay extremism."

Although the first few hours were peaceful, some 100 youths tried to push past barricades to reach the Champs Elysee. Protesters went on to block a major intersection leading to the presidential palace.

Movement finds a face

The movement against gay marriage has been fronted by Parisian socialite Virginie Tellenne, who goes by the name "Frigide Barjot." The moniker is a play on the name of French film actress Brigitte Bardot.

The campaign against gay marriage and adoption rights for single-sex couples was initiated by the Catholic Church, with the country's conservative opposition adding its support belatedly.

Opponents of the law, which has been championed by President Francois Hollande and his Socialists, accuse the president of stifling discussion on the issue and are calling for a referendum.

France's Senate, set to consider the bill in April, is expected to pass the legislation.

rc/kms (AFP, AP, Reuters)