diff --git a/includes/common.inc b/includes/common.inc
index 7af684578d799f241b53f3dc3c5b0edc6d80c443..513b6fc9fafc614a6f251bcd7922d48c3abb6378 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -320,6 +320,7 @@ function drupal_goto($path = '', $query = NULL, $fragment = NULL, $http_response
  * Generates a site off-line message
  */
 function drupal_site_offline() {
+  drupal_maintenance_theme();
   drupal_set_header('HTTP/1.1 503 Service unavailable');
   drupal_set_title(t('Site off-line'));
   print theme('maintenance_page', filter_xss_admin(variable_get('site_offline_message',
diff --git a/includes/menu.inc b/includes/menu.inc
index 0750dddcccd5e2ba4cb6fdde358ffe340fc70452..3ab496bfd880a3bd391b0ea27a43a804e2f4a5df 100644
--- a/includes/menu.inc
+++ b/includes/menu.inc
@@ -305,6 +305,10 @@ function menu_get_item($path = NULL) {
  * Execute the page callback associated with the current path
  */
 function menu_execute_active_handler() {
+  if (_menu_site_is_offline()) {
+    return MENU_SITE_OFFLINE;
+  }
+
   if ($item = menu_get_item()) {
     if ($item->access) {
       if ($item->file) {
@@ -1462,3 +1466,28 @@ function menu_path_is_external($path) {
   $colonpos = strpos($path, ':');
   return $colonpos !== FALSE && !preg_match('![/?#]!', substr($path, 0, $colonpos)) && filter_xss_bad_protocol($path, FALSE) == check_plain($path);
 }
+
+/**
+ * Returns TRUE if the site is off-line for maintenance.
+ */
+function _menu_site_is_offline() {
+  // Check if site is set to off-line mode
+  if (variable_get('site_offline', 0)) {
+    // Check if the user has administration privileges
+    if (!user_access('administer site configuration')) {
+      // Check if this is an attempt to login
+      if (drupal_get_normal_path($_GET['q']) != 'user') {
+        return TRUE;
+      }
+    }
+    else {
+      $offline_message = t('Operating in off-line mode.');
+      $messages = drupal_set_message();
+      // Ensure that the off-line message is displayed only once [allowing for page redirects].
+      if (!isset($messages) || !isset($messages['status']) || !in_array($offline_message, $messages['status'])) {
+        drupal_set_message($offline_message);
+      }
+    }
+  }
+  return FALSE;
+}