OKLAHOMA CITY -- A U.S. federal appeals court ruling Friday that Oklahoma's ban on gay marriage is unconstitutional spurred celebration among gay rights activists but sparked sharp anger among Republican leaders in a conservative state that prides itself on being the buckle of the nation's Bible Belt.

A three-judge panel of the 10th U.S. Circuit Court of Appeals in Denver upheld a federal judge's ruling striking down Oklahoma's gay marriage ban, which had been approved by more than 75 per cent of voters in 2004.

The court put its 2-1 ruling on hold pending an appeal, meaning same-sex couples won't be allowed to marry in Oklahoma for now.

"Today's ruling is another instance of federal courts ignoring the will of the people and trampling on the right of states to govern themselves," Gov. Mary Fallin said. "In this case, two judges have acted to overturn a law supported by Oklahomans."

She said she hoped the decision was overturned and pledged to "fight back against our federal government when it seeks to ignore or change laws written and supported by Oklahomans."

Friday's decision marks the second time the federal appeals court has found the U.S. Constitution protects same-sex marriage.

In June, the same three-judge panel ruled that Utah's ban on same-sex marriage violates the Constitution, a decision that is also on hold. That was the first time an appellate court determined that the U.S. Supreme Court's decision striking down the Defence of Marriage Act meant states couldn't deny gays the ability to wed.

In its landmark ruling, the Supreme Court ordered the federal government to recognize state-sanctioned marriages but it stopped short of declaring same-sex marriages legal nationwide. Since then, however, state gay marriage bans have been falling around the country. Gay and lesbian couples can now marry in 19 states and Washington, D.C.

On Friday, the U.S. Supreme Court issued a stay in the Utah case that will require more than 1,000 same-sex married couples to wait longer for state benefits. Also Friday, Colorado's state Supreme Court ordered Denver's clerk to stop issuing marriage licenses to gay couples while the state's stricken ban is appealed.

Sharon Baldwin and Mary Bishop filed the Oklahoma lawsuit in 2004 shortly after 76 per cent of Oklahoma voters approved a constitutional ban on gay marriage. After an appeals court ruled in 2009 that the couple lacked standing, they filed an amended complaint listing as the defendant the Tulsa County Court Clerk, since that is the person who issues marriage licenses.

"There are so many gay and lesbian Oklahomans who are celebrating, and they have every right to, because this is a victory for all of us," Baldwin said.

A second claim, by Gay Phillips and Susan Barton, who had a civil union in Vermont and were legally wed in Canada, challenges a section of the Defence of Marriage Act that says individual states don't have to recognize same-sex marriages performed in other jurisdictions.

"We are so grateful that the 10th Circuit understands what more and more people across this country are beginning to realize -- that gay and lesbian people are citizens who should enjoy the same rights as straight people under the law," Baldwin and Bishop said in a statement.

Attorneys representing the clerk said they were considering their options. They noted the panel's dissenting judge argued that changing the definition of marriage should belong to Oklahoma residents, not a federal court.

"Every child deserves a mom and a dad, and the people of Oklahoma confirmed that at the ballot box when they approved a constitutional amendment that affirmed marriage as a man-woman union," said Byron Babione, senior attorney for the Alliance Defending Freedom, which is defending the county clerk.

- Riccardi reported from Denver. Associated Press writer Tim Talley contributed to this report.