Greek parliament overnight approved a bill that will also allow same-sex couples to adopt children, making socially conservative Greece one of the first Orthodox Christian countries to allow such unions.

"This is a milestone for human rights, reflecting today's Greece - a progressive, and democratic country, passionately committed to European values," said Prime Minister Kyriakos Mitsotakis, who had urged lawmakers to pass the bill on Thursday.

The law, celebrated by dozens of people on the streets of Athens but opposed by the Orthodox Church and many right-wing politicians, will take a few days to become official.

That has not stopped couples, many who have waited years to get married, to make the first steps.

A gay couple in Athens on Friday announced their plan to wed in a newspaper, required for all marriages under Greek law.

They contacted the municipality of Nea Smirni in Athens last week asking for the necessary supporting documents, said Constantinos Anagnostopoulos, a vice mayor in charge of civil marriages in the municipality told state TV.

"From here on, we'll follow the ministry's go ahead and run the first wedding," he said.

The vote was welcomed by dozens of countries.

"We celebrate this historic moment together with the people, parliament and government of Greece," read a joint statement by 28 embassies in Greece, from the Netherlands to South Africa and Argentina.

At home, the topic of same-sex marriage divides Greece, where the Church and the right have long opposed reform. Residents of Athens expressed mixed opinions.

"The concept of family has collapsed, we have individual rights, but these cannot be institutionalised and affect everyone in society," said Eleni Parasi, a 50-year-old civil servant.

Greece has lagged behind other EU countries on LGBT+ rights for decades. But the country has made progress in recent years.

In 2015, it allowed civil partnership among same-sex couples, and in 2017 gave legal recognition to gender identity. Two years ago it banned conversion therapy for minors aimed at suppressing a person's sexual orientation.

"Since they wanted to be legal and get married, they did well and the bill was passed," said 68-year-old pensioner Thimios Tsakonitis. "Let them be equal."

(Reporting by Renee Maltezou and Angeliki Koutantou; Additional reporting Stamos Prousalis; editing by Edward McAllister, William Maclean)

By Renee Maltezou and Angeliki Koutantou