Croatian voters have backed proposals to ban same-sex marriages in a referendum.Two-thirds of those who voted approved changes to Croatia's constitution to define marriage as a union between a man and a woman, BBC reported.A government spokesperson confirmed that the constitution would now have to be changed accordingly.Saturday saw hundreds of gay rights supporters protest in Zagreb.A petition backing the referendum, drawn up by a Catholic group, received more than 700,000 signatures.The referendum asked the question: "Do you agree that marriage is the union between a man and a woman?"Almost 90% of Croatia's population of 4.4 million are Roman Catholics and the Church had strongly urged a "Yes" vote.The vote also received support from 104 members of Croatia's 151-seat parliament.President Ivo Josipovic said he was disappointed but not surprised by the outcome of the vote. "The referendum result must not be the reason for new divisions," he warned.The government, human rights groups and prominent public figures had all spoken out against the referendum, urging people to vote no.Prime Minister Zoran Milanovic had argued that the referendum threatened people's right to happiness and choice. His government has pledged to push forward in the coming days proposals to give greater rights to same-sex couples.But leaders of the opposition HDZ party supported the referendum.Gay rights protesters, under a heavy police presence, marched for an hour through the the capital Zagreb on Saturday and unfurled a giant rainbow flag outside parliament."We urge voters... to protect minority rights so that no-one in Croatia becomes a second-class citizen," activist Sanja Juras told a crowd in the city.The plan for a referendum was allowed parliamentary scrutiny after a Catholic group called "In the Name of the Family" gathered enough signatures to pass the required threshold of support."Marriage is the only union enabling procreation. This is the key difference between a marriage... and other unions," said Croatia's Cardinal Josip Bozanic in a letter read out in churches.Correspondents say attitudes towards gay rights in Croatia - which joined the European Union in July - are slowly changing.In Zagreb's first gay pride parade in 2002, dozens of participants were beaten up by extremists.Parades are now held regularly although under heavy security.ANN.Az