A couple is seen kissing as people celebrate Germany's parliament legalising the same-sex marriage in front of the Brandenburg Gate in Berlin, Germany June 30, 2017. [Photo/Agencies]

The move brings Germany into line with many other European nations including France, Britain and Spain and follows Merkel's surprise decision this week to allow her lawmakers to follow their own conscience rather than the party line on the issue. Merkel, daughter of a Protestant pastor, voted against the bill.

Hundreds of gay activists, some with painted faces, celebrated outside the Bundestag lower house of parliament after the vote, waving rainbow flags and placards that read "Marriage for all - make love for all".

"This is simply a historic day for Germany," said Soeren Landmann, a marriage equality activist.

"Today, thousands of same-sex couples were given equality, and the two-class society in matters of love was abolished. Germany can really rejoice today."

The vote has particular resonance in Germany as it unwinds a legacy of virulent homophobia. Earlier this year parliament agreed to grant compensation to thousands of gay men jailed under a 19th century law that was strengthened by the Nazis and only dropped in 1969 when homosexuality was decriminalised in West Germany.

Merkel, who is seeking a fourth term in a national election on Sept. 24, said she had voted against the bill because she believed that marriage as defined under German law was between a man and a woman.

But she said her decision was a personal one, adding that she had become convinced in recent years that same-sex couples should be allowed to adopt children.

"I hope that the vote today not only promotes respect between the different opinions but also brings more social cohesion and peace," she said.

A survey by pollster INSA for daily Bild showed this week that three quarters of Germans favoured the legalisation of same-sex marriage.

Lawmakers voted by 393 votes in favour of same-sex marriage to 226 against, with four abstentions.

The landmark vote came about almost by chance after Merkel announced on Monday she would allow lawmakers to vote on same-sex marriage according to their individual conscience, drawing the ire of some in her traditionally Catholic conservative bloc.