Authorities on the small Aegean island of Tilos early on Tuesday officiated over the first same-sex civil marriages ever held in Greece, the local mayor and one of the newlyweds said.
"The ceremony took place this morning," Tilos mayor Anastasios Aliferis told AFP. "Two couples were married."
Greek gay rights groups exploited a loophole in a 1982 law that does not specify that a civil union must involve a man and a woman.
"Everything went well, around twenty residents and relatives were present," said 47-year-old Evangelia Vlami of Greece's main homosexual association, Olke, who married a woman of similar age.
"A step forward for equality has been taken," she added.
Two men of undisclosed identity and age were also married on Tuesday.
Hours later, the prosecutor of Rhodes island -- the administrative centre of the Dodecanese island group -- called on the mayor to annul the marriage.
The prosecutor also opened a preliminary inquiry to determine whether the mayor can be prosecuted for breach of duty, a judicial source said.
There was no immediate reaction to the marriage from the Greek government or the influential Greek Orthodox Church, both of whom steadfastly oppose gay marriage.
Greece's top prosecutor last week warned that any such move by local authorities would be "not only void but also illegal."
The country's justice minister has also warned that gay marriages are outside the law.
"People can do whatever they want but it would not be legal," Minister Sotiris Hatzigakis told state television NET last week.
But Mayor Aliferis, a socialist, said there was no legal obstacle to the ceremony taking place.
"We have taken part in the struggle for the defence of human rights," he told private Flash Radio.
Gay activists launched the initiative after the government introduced a cohabitation law for unmarried couples that made no reference to homosexuals.
Homosexuals have sought greater visibility and voice in recent years, holding the country's first Gay Pride event in 2005.