U.S. federal land managers have released all 400 head of cattle rounded up on public land in southern Nevada from a rancher who has refused to recognize their authority.

The Bureau of Land Management took the action Saturday afternoon after hundreds of protesters, including militia and members of the conservative tea party members, showed up at corrals to demand the animals' return to rancher Cliven Bundy.

The fight has widened into a debate about states' rights and federal land-use policy. The tea party advocates a smaller role for the federal government in public life.

The agency revoked Cliven Bundy's grazing rights after he stopped paying grazing fees and disregarded court orders to remove his animals.

The bureau issued a brief statement saying the cattle were released "due to escalating tensions."