Croatians are voting in a referendum Sunday sought by majority Roman Catholics who want same-sex marriage outlawed in the new EU nation's constitution. Croatia's center-left government has argued for gay rights.

Sunday's vote - the first citizens'-initiated referendum since Croatia's independence from former Yugoslavia in 1991 – is the result of a church-led campaign begun in May. Croatia joined the EU in July

Using the title "In the Name of the Family", campaigners collected more than 700,000 signatures to initiate the referendum. They have urged followers among Croatia's 4.2 million inhabitants to vote "yes" to define marriage as a "union between a woman and a man."

Pollsters predict that about 70 percent will do so, with the rest opposed.

The Social Democratic government of Prime Minister Zoran Milanovic and human rights activists have urged voters to cast "no" votes.

The 28-nation EU bloc as a whole treats same sex marriage as a sovereign issue for individual nations to decide.

Pro and contra

Police guarded some 1,000 gay rights supporters in Zagreb on Saturday as they called for a "no" vote and argued that a constitution confined to traditional marriage would be discriminatory.

Gay rights activist Sanja Juras told protestors: "We urge voters … to protect minority rights so that no one in Croatia becomes a second-class citizen."

In a letter read out in churches, Croatia's Cardinal Josip Bozanic said "marriage is the only union enabling procreation."

"This is the key difference between a marriage … and other unions," he wrote.

Gay pride parades under police guard have become more common in Croatia since 2002 when dozens of participants were beaten up by extremists during the first rally in Zagreb.

Croatia's constitution currently does not define marriage. The referendum result will be legally binding. The vote does not require a majority voter turnout to be valid.

ipj/mr (dpa, AFP)