PARIS (AFP) - France on Saturday became the 14th country to legalise same-sex marriage after President Francois Hollande signed the measure into law following months of bitter debate and demonstrations.
Mr Hollande acted a day after the Constitutional Council threw out a legal challenge by the right-wing opposition, removing the last obstacle to passing the bill into law. The legislation also legalises gay adoption.
But while gay rights groups hailed the move, opponents of the measures have vowed to fight on. Mr Hollande made "marriage for all" a central plank of his presidential election campaign last year.
On Friday, he tried to turn the page on months of bitter opposition to the measures, arguing it was "time to respect the law and the Republic".
And he warned that he would not tolerate any resistance.
"I will ensure that the law applies across the whole territory, in full, and I will not accept any disruption of these marriages," said the Socialist president.
Meanwhile, the Socialist mayor of the southern city of Montpellier - known to homosexuals as the French San Francisco - will officiate the municipality's first gay marriage on May 29, her office said on Saturday.
The nuptials in Montpellier are expected to be the country's first legal gay marriage.
Marriages in France must be civil ceremonies performed in town halls, most of which take several weeks to process applications. Couples can then hold a religious ceremony.
"We have published with my partner our (marriage) bans this morning and we can now think about the preparations" for the Montpellier wedding, said gay activist Vincent Autin, 40, who is going to marry his 30-year-old partner Bruno after seven years as a couple.
"I am overwhelmed with immense happiness. We are inviting all the French people to attend the wedding," Mr Autin added, explaining that the city had agreed to put up a giant screen if a huge crowd turns out for the event.
The gay marriage and adoption law, however, has come into force after months of acrimonious debate and massive opposition protests, which occasionally spilled over into violence.
Although the Constitutional Council approved the bill on Friday, the International Day Against Homophobia, opponents, who maintain marriage is only between a man and a woman, have vowed not to give up.
They have called a major protest rally for May 26 in Paris. Previous demonstrations have drawn hundreds of thousands of people marching through the streets of the French capital.
In April, the main right-wing opposition UMP party of former president Nicolas Sarkozy challenged the measures on constitutional grounds immediately after deputies passed the bill in parliament.
But Friday's statement by the Constitutional Council said same-sex marriage "did not run contrary to any constitutional principles", and that it did not infringe on "basic rights or liberties or national sovereignty".
Reacting to the ruling Friday, UMP party chief Jean-Francois Cope told TF1 television: "It is a decision that I regret, but that I respect." However, an anti-gay marriage figure known as Frigide Barjot - a play on the name of film star Brigitte Bardot and translates as Frigid Loony- called the new law "a change in civilisation".
Late Friday, between 200 and 300 protesters gathered in central Paris to denounce the ruling backing the bill and called on Hollande to resign. One police officer was injured after a flammable liquid was thrown in his face.
For gay rights groups the French law legalising same-sex marriage is a watershed.
"Now it's celebration time," said spokesman Nicolas Gougain of the LGBT association representing the lesbian, gay, bisexual and transgender communities.
But gay rights watchdog SOS Homophobie added: "Our country has taken a great step forward today although it's regrettable that it was taken in a climate of bad faith and homophobic violence." The issue of gay marriage has divided France, which is officially secular but overwhelmingly Catholic.
Last year, the proposals seemed to enjoy solid majority backing among French voters.
But as the opposition campaign got into gear, more recent polls indicated a shift of opinion to the extent that the electorate is now fairly evenly split on both gay marriage and adoption.
Among the countries that have already approved same-sex marriage are eight other European nations - Belgium, Denmark, Iceland, the Netherlands, Norway, Portugal, Spain and Sweden.