AngularJS - Form for dynamic created checkbox

I'm Creating Multiple checkbox using ng-repeat. How to validate such form if any one of checkbox is checked using form validation?

<div class="checkbox" ng-repeat="nereg in northeastRegion track by $index" ng-click="nereg.selected = !nereg.selected">
  <input type="checkbox" ng-checked="nereg.selected" >
  <label for=""></label>
</div>

JS

$scope.northeastRegion = [{
        title: 'New England',
        selected: false
      },
      {
        title: 'New York Metro',
        selected: false
      },
      {
        title: 'Philly Tri-State',
        selected: false
      },
      {
        title: 'Upstate New York',
        selected: false
      },
      {
        title: 'Washignton',
        selected: false
      }
    ];