JUNEAU, Alaska (AP) - Five gay couples are challenging Alaska's ban on same-sex marriage as unconstitutional.

A lawsuit on behalf of the couples was filed in federal court in Anchorage on Monday.

Alaska voters in 1998 approved a state constitutional amendment defining marriage as being between one man and one woman. But in the past year, the U.S. Supreme Court has struck down a provision of the federal Defense of Marriage Act that prevented legally married same-sex couples from receiving a range of federal benefits. Federal courts have struck down state constitutional bans in a number of states, though appeals were pending.

The lawsuit says the ban deprives the couples of due process and equal protection under the U.S. Constitution. Four of the couples were married outside Alaska, and one couple is unmarried.

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