SAN FRANCISCO (REUTERS) - Same-sex marriages were set to resume in California on Friday, after the 9th Circuit Court of Appeals issued a surprise order lifting an injunction preventing the unions.

The order came in response to an opinion released Wednesday by the United States (US) Supreme Court that effectively killed a voter-approved ban on same-sex marriages in the state.

Within moments of the ruling, couples, officials and activists began to converge on San Francisco City Hall, where unions were due to resume immediately.

"On my way to S.F. City Hall," tweeted the state's attorney general, Ms Kamala Harris. "Let the wedding bells ring!" MsHarris arrived with her arm around a key lawyer in the case, as the couple at the heart of a case challenging the state's ban waited eagerly for their marriage licence to be issued.

"This is really a great day," said MsCindy Stier, who with her fiancee Kristin Perry filed the lawsuit against Proposition 8, the ballot initiative that outlawed same-sex marriage in California in 2008.

The 9th Circuit had been expected to wait 25 days before lifting the injunction so the Supreme Court would have time to release a formal order. But the judges decided to act instead on Friday, a move that would allow the marriages to begin in advance of Gay Pride weekend.

"The stay in the above matter is dissolved effective immediately," the 9th Circuit Court of Appeals said in its ruling.