New Zealand became the first Asia-Pacific country to legalise same-sex marriage Wednesday after a decades-long campaign, a historic decision celebrated with parties across the gay community.

A parliamentary vote overwhelmingly backed a move to amend the 1955 Marriage Act 77-44 to describe matrimony as a union of two people regardless of their sex, sexuality or how they choose to identify their gender.

"It is about saying these lives matter, our society is big enough for us," gay Green Party MP Kevin Hague told parliament.

The lawmaker behind the reform, Louisa Wall, a gay member of the centre-left Labour Party, said the New Zealand legislation should pave the way for reform in other countries in the region.

"The law unfortunately has treated homosexual New Zealanders as less than human, as less than equal citizens," she told AFP. "What this bill will do is ensure the state does not discriminate against any citizen."

On the capital's Cuba Street entertainment strip, gay venues such as the San Francisco Bath House and S&M's held parties while screening Wednesday night's vote live.

Parliament's public gallery was booked out due to overwhelming demand and a big screen was erected in an overflow room near the debating chamber to accommodate hundreds of extra onlookers.

"There's going to be parties everywhere," LegaliseLove Wellington co-ordinator Joseph Habgood said ahead of the vote.

The change makes New Zealand the 13th nation globally to allow gay marriage, according to Human Rights Watch (HRW).

Australia rejected a similar proposal last September and the issue has prompted heated debate in the United States since President Barack Obama made support for same-sex unions a prominent part of his second-term agenda.

With Britain and France both appearing set to adopt same-sex marriage soon, Wall said a "global conversation" on gay rights was occurring, which should prompt changes in nations such as Tonga and Samoa, where homosexuality is still illegal.

Opinion was divided on Cuba Street ahead of the vote.

"If some people are allowed to do it, then all people should be allowed to do it," Christina Hroch said "I haven't met anyone that would be against it."

But Suzy Prime was "totally opposed" to the change, raising concerns about the impact on children raised in same-sex marriages.

"I don't think there's a need for marriage," she said. "We already have a law that they can be together with their civil rights. I don't have a problem with that but I don't think it's right to go beyond that and allow marriage."

New Zealand decriminalised homosexuality in 1986 and since 2005 has allowed same-sex civil unions.

HRW lists the countries that currently allow same-sex marriage as The Netherlands, Belgium, Canada, South Africa, Argentina, Spain, Portugal, Norway, Sweden, Denmark, Iceland and Uruguay, which changed the law this month.

Here is a breakdown of nations with similar laws on the books:

- NETHERLANDS: On April 1, 2001 the Netherlands became the first country in the world to legalise same-sex marriage, with the same rights as heterosexuals. Includes the right to adoption.

- BELGIUM: Homosexual couples in Belgium have almost the same rights as heterosexuals. They won the right to marry in 2003 and in 2006 parliament voted into law a bill allowing homosexual couples to adopt children.

- SPAIN: In 2005 Spain became the third member of the European Union to pass a law allowing same-sex marriages. Gay couples can adopt children, whether they are married or not.

- CANADA: Canada adopted a national law allowing gays to marry and adopt in July 2005 though most provinces had already allowed same-sex unions before that date.

- SOUTH AFRICA: The country legalised same-sex unions and adoptions by gay couples in November 2006, becoming the first African nation to do so.

- NORWAY: A 2009 law allowed homosexuals to marry and adopt children. Civil partnerships have existed in the country for 20 years.

- SWEDEN: Sweden's homosexuals have been allowed to wed in religious or civil ceremonies since May 2009.

- PORTUGAL: Under a 2010 law Portugal legalised gay marriage, while excluding the right to adoption.

- ICELAND: Prime Minister Johanna Sigurdardottir married her long-time partner in June 2010 as a new law legalising homosexual marriages came into force. Same sex couples who have lived together for at least five years have had the right to adopt children since 2006.

- ARGENTINA: Gays in Argentina became the first on the South American continent to be able to wed and adopt, after legislation passed on July 14, 2010.

- DENMARK: Denmark, the first country in the world to allow gay couples to enter into civil unions in 1989, voted overwhelmingly in favour of allowing homosexuals to marry in the state Evangelical Lutheran Church in June 2012.

- URUGUAY: Uruguay voted this month to allow same-sex marriages nationwide, making it only the second Latin American country to do so.

-- PARTIAL RULES --

Gay couples can marry in nine US states, as well as in the capital Washington, while parts of Mexico and Brazil also allow same-sex marriage.

-- EXPECTED SOON --

- FRANCE: France's upper house Senate voted last week to approve a landmark bill granting homosexual couples the right to marry and adopt, putting the bill on track to become law within weeks.

- BRITAIN: British lawmakers voted in February in favour of controversial legislation allowing gay marriage despite fierce opposition from members of Prime Minister David Cameron's Conservative party.

The bill must next be scrutinised by a committee of lawmakers and then go before the upper chamber the House of Lords before becoming law.

-- CIVIL UNIONS --

A number of other countries have adopted laws that recognise civil partnerships and give couples more or less the same rights as heterosexuals.

Countries to have recognised civil unions without yet accepting gay marriage include Germany (2001), Finland (2002), the Czech Republic (2006), Switzerland (2007) and Colombia and Ireland (both 2011).