Go to the advanced search page.
Select the "Object type" and "Product type", add one or more filters if you wish to exclude a specific group of objects, and finally click "Select all results".
Once you have selected all the results, click on "Actions", then "Delete".
A window will appear on your screen; in the field provided, type the word "Delete" using your keyboard, then click the "Delete" button.
Warning : This action is irreversible.