By Colleen Jenkins

WINSTON-SALEM, North Carolina (Reuters) - A North Carolina official accepted marriage license applications on Tuesday from 12 same-sex couples - an unprecedented move in the U.S. South that advocates hoped would spur others to challenge state bans on such weddings.

Drew Reisinger, the elected register of deeds for Buncombe County, which includes Asheville, did not immediately issue the licenses as two local officials in New Mexico and Pennsylvania have done.

But he questioned the legality of North Carolina's prohibition against same-sex marriages in light of the U.S. Supreme Court decision in June that struck down a key part of the 1996 Defense of Marriage Act denying benefits to same-sex married couples.

"Why are we denying same-sex couples in North Carolina the dignity and the legal acknowledgement granted to heterosexual couples here or same-sex couples in other states?" Reisinger said in a letter seeking a formal opinion from the state attorney general.

"Marriage rights are civil rights and should not vary based on where you live," he added.

North Carolina Attorney General Roy Cooper, a Democrat, said this week that he personally supports gay marriage but is committed to defending the state ban in a pending lawsuit.

Gay marriage opponents see local officials who issue licenses to same-sex couples residing outside the 13 states and District of Columbia that have legalized gay marriage as trying to make an end-run around the law.

"It is very clear that Registers of Deeds in North Carolina have no legal authority to either accept applications for nor issue marriage licenses to same-sex couples," said Tami Fitzgerald, executive director of the North Carolina Values Coalition.

In 2012, North Carolina became the last state in the South, where support for gay marriage has lagged behind other parts of the country, to add a voter-approved ban on gay marriage to its constitution.

Twenty-nine U.S. states have constitutional amendments defining marriage as between a man and a woman, and six other states have laws that do so.

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On Tuesday, a spokeswoman for Cooper said his office is not typically involved in issuing or approving marriage licenses, leaving unclear whether the attorney general will heed Reisinger's request for clarification on the issue.

"The State Constitution says that these marriage licenses cannot be issued, and this is the law unless the Constitution is changed, or the court says otherwise," spokeswoman Noelle Talley said in an email.

In Pennsylvania, Attorney General Kathleen Kane, also a Democrat, said in July she would not defend her state's ban on gay marriage in a federal court case there, calling the ban "wholly unconstitutional."

Gay marriage advocates in North Carolina said they hoped Cooper's legal analysis of his state's ban would evolve to match his personal stance on marriage equality.

"We're hopeful that Attorney General Cooper will take a similar position" to Kane's and refuse to defend the ban, said Jasmine Beach-Ferrara, executive director of the Campaign for Southern Equality.

The experience in Buncombe County on Tuesday was a refreshing change for Brenda Clark and Carol McCrory, an educational consultant and retired lawyer who have been together for 25 years. Their four previous attempts to obtain a marriage license had been rejected outright.

This time, Reisinger held their hands and told them he planned to ask the attorney general for permission to grant the couple a license to wed in their home state, McCrory said.

"It was really emotional for us, to finally take one step forward," she said. "We were amazed that he had the courage to do this, at great personal risk."

Reisinger said he does not intend to break the law.

"I just don't know how to proceed because it seems like the North Carolina constitution no longer protects the rights of all people like our United States constitution grants us," he said.

(Editing by Gunna Dickson)