Croatians have voted by a large majority to back traditional marriage in a referendum.
On Sunday, two-thirds of those who voted supported changing the country’s constitution to define marriage as a union between a man and a woman.
Over 700,000 people signed a petition backed by the Roman Catholic Church asking for a referendum on the issue.
“Marriage is the only union enabling procreation”, said Croatia’s Cardinal Josip Bozanic.
People were asked in the public vote: “Do you agree that marriage is matrimony between a man and a woman?”
A spokesman for the Government confirmed that the constitution would now be changed, as it currently does not define marriage.
But human rights groups have said they will appeal against the referendum, saying it goes against basic human rights in the country.
The petition was collected following the unveiling of a Government Bill which would enable gay couples to register as “life partners”, and concerns were raised that same-sex marriage would be next.
The number of signatures crossed a threshold which meant parliament had to consider the issue.
Two-thirds of parliament voted in favour of holding the referendum.
Zeljka Markic, the leader of the group which initiated the petition, told the media that the people have a right to say what they think marriage is.
She said: “We wanted to be sure that, if citizens decide so, by introducing marriage as the union of life between a man and a woman we will prevent any government to change the substance of marriage without consulting the citizens of Croatia”.
The Prime Minister and the President of Croatia are both disappointed with the outcome of the referendum.
In the UK two-thirds of a million people have signed a petition, started by campaign group Coalition for Marriage, which says marriage should be defined as between one man and one woman.
But legislation which allows same-sex couples to marry in England and Wales received Royal Assent in July this year.
The Republic of Ireland is to hold a referendum on gay marriage in 2015.