Catholic and conservative Croatia has voted to ban same-sex marriage by a strong majority as activists warned Monday that the poll was a step back for the EU's newest member.

At a referendum on Sunday, almost 66 percent of voters said "yes" to amending the constitution limiting the definition of marriage as a "union between a woman and a man".

Currently, Croatia's constitution does not define marriage.

"This is very dangerous move through which a democratic institution was actually abused for a collapse of democracy," prominent human rights activist Zoran Pusic told AFP.

"This amendment is against the spirit of the constitution which should protect and secure equality, freedom and justice."

Pusic added that the vote targeted a minority group whose rights do not endanger the rights of others and such trends are "extremely dangerous for a society".

The referendum was held after a Church-backed group in May collected almost 700,000 signatures seeking a nationwide vote on the definition of marriage.

Croatia's conservatives feared that after the centre-left government announced a bill enabling gay couples to register as "life partners", same-sex marriage would be next.

Although passions ran high in Croatia ahead of the vote, with the Church-backed "yes" camp citing the defence of traditional family values and their opponents accusing them of discrimination against gays, the turnout was rather low.

Only slightly more than one-third of the 3.8 million eligible voters cast ballots, among the lowest turnouts ever in Croatia's elections.

Under Croatian law, a referendum does not require a majority voter turnout to be valid, which means that a small number of ballots can decide on issues.

Political analysts estimated that a low turnout showed that despite a heated public debate, the majority of Croatians are concentrating on economic issues in a country hit by a long-lasting recession.

"Citizens want to live better and ... this seemed to them as squabbling which moved political elites away from what they see as fundamental problems," political scientist Zoran Kurelic estimated.

Conservative, Church-influenced society

Those backing same-sex marriage, said Sunday's result could pave the way for other conservative initiatives targeting minorities or on issues such as abortion.

Analysts also say the vote reaffirmed Croatia, which joined the European Union in July, as a conservative society strongly influenced by the Catholic Church. Almost 90 percent of Croatians are Roman Catholics.

Late Sunday, the leader of the "In the Name of the Family" group, Zeljka Markic, celebrated victory "this time for the protection of marriage, and next time for something else of the same importance." She did not elaborate.

Dragan Zelic, of the GONG rights group, labelled the referendum a "step backwards".

However, gay activists in a statement said the "family life of same-sex partners, with or without children, is a reality of our society, which no constitutional amendment, referendum or manipulation can change".

Attitudes towards gay rights have slowly become more liberal in Croatia since it hosted its first Gay Pride parade in Zagreb in 2002. Dozens of participants were beaten up by extremists at the time.

But gay rights marches are now staged regularly, though still under heavy security.

The issue is also discussed more openly in the media and homosexuals are less fearful of "coming out".

In 2003, Croatia adopted a law recognising same-sex couples who have lived together for at least three years, although apart from official acknowledgement, the measure grants them few rights.

Sunday's vote was the first citizen-initiated referendum since Croatia's independence from the former Yugoslavia in 1991.

Such vote can be called if at least 10 percent of the electorate sign a petition for a referendum.

On Monday, a group of Croatia's 1991-1995 war veterans said they would petition for a referendum that would reduce minority rights, targeting ethnic Serbs.

They want to narrow the official use of minority languages and alphabets to areas where they make up at least 50 percent of the population.

The move was prompted by the introduction of official signs written in the Cyrillic Serb alphabet alongside the Latin alphabet for Croatians in the eastern city of Vukovar.