A lesbian couple who spearheaded a fight for same-sex marriage in California became the first Friday to tie the knot hours after a ban was lifted, following a landmark US Supreme Court ruling.

Cheers erupted at San Francisco City Hall after Kristin Perry and Sandy Stier exchanged vows, in a ceremony conducted by California Attorney General Kamala Harris.

"I now declare you spouses for life," said Harris, after the couple exchanged rings and vows in front of a hastily-assembled gathering. "I could not be more honored to stand here today."

"We have waited a long long time for this day," said Stier after the ceremony, the first gay wedding since a brief period in 2008 when California allowed same-sex marriage but then banned it under a close-run referendum.

The ceremony came only an hour or two after the Ninth Circuit Court of Appeals in San Francisco lifted the ban on same-sex marriages, imposed under the so-called Prop 8 ballot measure, with immediate effect.

Many observers thought it could be several weeks before marriages would resume in the famously liberal western US state, but the appeals court announced the ban was lifted in a brief ruling posted online.

"The stay in the above matter is dissolved effective immediately," the ruling read, prompting an explosion of online celebration, and hasty wedding ceremony preparations.

Perry and Stier were the first to get married in San Francisco, but they were followed by a long line of other same-sex couples, who rushed to City Hall after news of the unexpectedly early court decision broke.

"Kris and I fell in love 14 years ago. We knew that our relationship would last ... and wanted our love to last and to be dignified by the institution of marriage," said Stier. Perry told the crowd: "This is the first day of the rest of our lives together, and we could not be more elated by your being here."

Perry and Stier were the plaintiffs in the initial action challenging Prop 8, which wound its way through the legal system before eventually being heard by the top US court.

The Supreme Court ruled that supporters of Prop 8 lacked the proper standing to appeal a lower-court judgment that declared the measure unconstitutional.

The ruling essentially allowed the original federal court ruling to stand, striking down Prop 8.

Supporters of Prop 8 have vowed to pursue their efforts to have the ban -- backed by 52 percent of Californians five years ago, with 48 percent against -- re-enforced.

ProtectMarriage.com, the organization which supported Prop 8, slammed Friday's court decision.

"This outrageous act tops off a chronic pattern of lawlessness, throughout this case, by judges and politicians hell-bent on thwarting the vote of the people to redefine marriage by any means, even outright corruption," it said.

It added: "The resumption of same-sex marriage this day has been obtained by illegitimate means. If our opponents rejoice in achieving their goal in a dishonorable fashion, they should be ashamed."

"It remains to be seen whether the fight can go on, but either way, it is a disgraceful day for California."

A short time after the San Francisco ceremony, the first gay wedding in Los Angeles was conducted by outgoing Mayor Antonio Villaraigosa, with Paul Katami and Jeff Zarrillo exchanging rows in the city hall.

At one point, the beaming mayor paused as he read out the vows for the two men to repeat after him, telling them: "I don't know about you, but I got goosebumps."

"Let me pronounce you married," he said after the couple had exchanged rings, and before they kissed for the first time as newlyweds.