A national gay-rights organization has filed a federal lawsuit on behalf of seven couples and two surviving spouses challenging Arizona's ban on same-sex marriage.

The suit filed Thursday by Lambda Legal claims banning gay marriage violates the couples' rights to equal protection and due process under the U.S. Constitution.

Arizona Attorney General Tom Horne, state Department of Health Services director Will Humble and Maricopa County Superior Court clerk Michael Jeanes are named as defendants in the complaint.

Jennifer Pizer, senior counsel for Lambda Legal, said the suit is also requesting Arizona legally recognize the marriages of the couples who wed in other states.

The suit is separate from a class-action lawsuit filed by four same-sex couples in January. That case was filed against Horne and Gov. Jan Brewer.