Dublin (AFP) - Ireland's new same-sex marriage law comes into force from Monday, six months after the country voted to allow gay unions in a historic referendum.

Existing same-sex marriages registered abroad will be immediately recognised in Ireland, while other couples can now submit their intention to marry.

"I felt I didn't have permission to say we were married but from now we will say it at every opportunity," said Vivian Cummins, 57, from Dublin who married his partner Erney in South Africa in 2009.

"I would never really admit by choice to being married because I didn't feel married in this country," he told AFP.

In May, Ireland voted 62.1 percent in favour of allowing marriage between two people "without distinction as to their sex", the first time anywhere that gay marriage has been legalised in a referendum.

It was a long journey for LGBT campaigners in the traditionally Catholic country that only decriminalised homosexual acts in 1993.

"After years of waiting for this day, it's just an extraordinary moment for us," said Senator Katherine Zappone, who lost a High Court case in 2006 to have her Canadian marriage to her wife recognised in Ireland.

The couple plan to bring their "marriage home" in a ceremony in January after Zappone proposed to her wife Ann Louise Gilligan live on national television after the referendum result was announced.

A total of 2,054 couples have entered a civil partnership since Ireland introduced the legal unions in 2011 but a further ceremony will be required to convert these into marriage, with just a few days notice.

Under Irish law, it is required to submit an "intention to marry" to authorities three months before a marriage.

- Longest engagement on Earth -

Those already in civil partnerships will only have to give five days notice under the new rules.

And the 187 couples who have applied for civil partnerships since the referendum will be able to get married instead, from as soon as Monday in some cases.

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"I think it's going to be massive," said wedding planner Marian Purcell of Gay Weddings Ireland.

Purcell has 15 same-sex weddings booked already and "a lot more in the pipeline" with enquiries from couples in America, Slovenia, Italy and England.

"It's going to be very exciting in the future. I don't think it will die down after the initial few, everyone loves a good wedding," she told AFP.

"People are seeing Ireland in a new light as an LGBT friendly country for honeymoons and holidays too."

But after a long campaign and several milestones, as the new legislation worked its way through parliament, campaigners are looking forward to weddings beginning.

"I suspect people must now be feeling like this is the longest engagement on Earth," said Colm O'Gorman, chief executive of Amnesty International Ireland and one of the leading "Yes" campaigners.

"We are at last at the stage where people are just getting on with their lives and marriages can happen."