Irish voters have resoundingly backed amending the constitution to legalize gay marriage, officials declared on Saturday after the world's first national vote on the issue.

The official results show 62.1 per cent voted in favour of the gay marriage referendum.

"Yes" supporters crowded into the courtyard of Dublin Castle to watch in blistering sunshine as results trickled in from around the country were shown on a large screen. They cheered with joy as the final tally was announced and then burst into a rendition of the national anthem.

"With today's vote we have disclosed who we are — a generous, passionate, bold and joyful people," Irish Prime Minister Enda Kenny said at a news conference.

"The people have answered the call of families and friends, of neighbours and new acquaintances," Kenny said.

"Yes to inclusion. Yes to generosity. Yes to love. Yes to equal marriage."

Applause rang out as former Labour Party head Eamon Gilmore walked into a counting centre draped in a rainbow flag. (Nahlah Ayed/CBC) The "yes" side wanted a resounding victory "and many of them feel that 62.1 per cent is the kind of result they could only hope for," reported CBC's Nahlah Ayed from Dublin.

Some political leaders in Canada approved of the result. Ontario Premier Kathleen Wynne, who is openly gay, and federal NDP Leader Tom Mulcair both tweeted congratulations.

"Especially proud of my Irish roots today. A clear progressive message from voters & resounding victory for equality," Mulcair tweeted.

The results and the high voter turnout — particularly among young people, many of whom traveled home from overseas to cast their ballots — suggest the country is moving away from its staunch conservatism and the influence of the Catholic Church, Ayed added.

"The power of the church, having waned, this is another indication that that waning continues," said Ayed.

The Catholic Church, which teaches that homosexual activity is a sin, saw its dominance of Irish politics collapse after a series of child sex abuse scandals in the early 1990s and limited its "no" campaigning to sermons to its remaining flock.

The archbishop of Dublin said the result presented a challenge.

"It is a social revolution. It's very clear that if this referendum is an affirmation of the views of young people, then the church has a huge task ahead of it," Archbishop Diarmuid Martin told national broadcaster RTE.

There's a rainbow over Dublin currently. Very appropriate. God clearly approves. <a href="https://twitter.com/hashtag/irelandreferendum?src=hash">#irelandreferendum</a> <a href="https://twitter.com/hashtag/IrelandVoteYes?src=hash">#IrelandVoteYes</a> <a href="http://t.co/ZEAo4H6JLA">pic.twitter.com/ZEAo4H6JLA</a> —@RobbieTravers

'A new country'

Political analysts who have covered Irish referendums for decades agreed that Saturday's results mark a stunning generational shift from the 1980s, when voters still firmly backed Catholic Church teachings and overwhelmingly voted against abortion and divorce.

"We're in a new country," said political analyst Sean Donnelly, who called the result "a tidal wave" that has produced pro-gay marriage majorities in even the most traditionally conservative rural corners of Ireland.

The vote has "shown the world ... that we stand up for what we believe in," said activist and mother Tara O'Toole, during an appearance on CBC News Network with her son, Fionn, who is gay.

"Ireland has done us proud today," she said. "Some people think we're a backward little country, but we're not."

The vote "means I don't have to go to another country to get married," added Fionn. "My country accepts me. It's really not more complicated than that."

Ireland voted heavily in favour of allowing same-sex marriage in a historic referendum in the traditionally Catholic country. (Cathal McNaughton/Reuters)

'A rainbow nation'

Ireland's deputy prime minister, Labour Party leader Joan Burton, said Ireland was becoming "a rainbow nation with a huge amount of diversity." She said while campaigning door to door, she met older gay people who described how society made them "live in a shadow and apart," and younger voters who were keen to ensure that Irish homosexuals live "as free citizens in a free republic."

The "yes" side ran a creative, compelling campaign that harnessed the power of social media to mobilize young voters, tens of thousands of whom voted for the first time Friday. The vote came five years after Parliament approved marriage-style civil partnerships for gay couples.

The pure joy of it. I'm so proud of Ireland today... We can all take pride in making history. Only sorry I can't be there to celebrate! —@Hozier

Those seeking a "no" outcome described their defeat as almost inevitable, given that all of Ireland's political parties and most politicians backed the legalization of homosexual unions.

David Quinn, leader of the Catholic think tank Iona Institute, said he was troubled by the fact that no political party backed the "no" cause.

"We helped to provide a voice to the hundreds of thousands of Irish people who did vote no. The fact that no political party supported them must be a concern from a democratic point of view," he said.