dynamically add boostrap rows and columns in mvc

I am having an issue with my foreach loop:

@foreach (var item in Model) 
{
    <div class="row">
        <div class="col-md-4 portfolio-item">
            <a href="@Html.DisplayFor(modelItem => item.UrlSlug)">
                <img class="img-responsive" src="http://ift.tt/1yI890U" alt="">
            </a>
            <h3>
                <a href="@Html.DisplayFor(modelItem => item.UrlSlug)">@Html.DisplayFor(modelItem => item.Title)</a>
            </h3>
            <p>@Html.DisplayFor(modelItem => item.ShortDescription)</p>
            @Html.ActionLink("Edit", "Edit", new { id = item.Id }) |
            @Html.ActionLink("Details", "Details", new { id = item.Id }) |
            @Html.ActionLink("Delete", "Delete", new { id = item.Id })
        </div>
    </div>

This method displays one big long list, however I only want to display three (3x) <div class="col-md-4 portfolio-item"> inside <div class="row"> after three portfolio items has been populated I then want to create another <div class="row"> and populate the next three <div class="col-md-4 portfolio-item">.

How can I achieve this?