Political observers from both sides of the campaign said the first ballot boxes to be counted on Saturday showed a clear majority of Irish voters had backed same-sex marriage.

"I think it's won," Equality Minister Aodhan O'Riordain told Reuters at the main count center in Dublin. "The numbers of people who turned out to vote is unprecedented. This has really touched a nerve in Ireland today."

Irish Health Minister Leo Varadkar, who was also watching ballots being tallied, said the Irish capital appeared to have voted around 70 percent in favor of legalizing gay marriage. Not a single district had yet reported a "No" majority, he added.

Strong leads for the "Yes" camp emerged in districts across Dublin, as well as in traditionally conservative rural areas.

David Quinn, a leading campaigner against gay marriage and director of the Iona Institute, a Catholic think tank, conceded defeat early on Saturday, telling national broadcaster RTE that it was "obviously a very impressive victory for the 'Yes' side."

He also pointed out that early tallies showed supporters of gay marriage had secured a victory "roughly in the region of two to one."

'Proud day to be Irish'

If the referendum passes, Ireland would become 19th country in the world to recognize marriage equality and the 14th in Europe - as well as the first to do so by popular vote.

"That makes us a beacon, a light to the rest of the world of liberty and equality. It's a very proud day to be Irish," said Varadkar, who came out as gay at the start of the government's campaign.

All Ireland's main political parties, including conservatives, support amending the constitutional definition of marriage. The Catholic Church campaigned strongly for a "No" vote.

Legalizing gay marriage would be a huge shift in Ireland, where the population of 4.6 million is predominantly Catholic. Homosexuality was illegal there until 1993.

Around 3.2 million people were eligible to vote in Friday's referendum, and reports suggest there was a higher-than-expected turnout.

The vote counting started at 9:00 a.m. local time (0800 UTC) in 43 constituencies across the country. A final nationwide result is expected later on Saturday.

nm/sms (AP, Reuters, AFP)