We will have to do some administrative settings change for deleting a bug. Log in with an account belonging to the admin group and navigate to the Administration page. Then go to the Parameters page. Navigate to Administration > Parameters > Administrative Policies.
Here you can see the allowbugdeletion parameter which will be set to off by default. Change the parameter to on and click Save Changes. The pages to edit products and components can delete all associated bugs when you delete a product or component. So, its always better to turn on this option before any such deletions can happen.
Here you will see a warning message stating that "You can't directly delete bugs, you must assign a bug to a component or product and delete it"
You can create a component in the product with the bugs we want to delete. Now find the bugs you want to delete and change their component to the one which you created. After adding all the bugs you want to delete into the component you had created, go back to the component list in the administration page > Administration > Products > Product > Edit Components. Now we can see an "Action" column on the right side of the table with all the components with a Delete link. Find component we created and click the associated "Delete" link.
We will be receive a confirmation page with a warning telling how many bugs will be deleted. You can view the bug list to verify or just click the "Yes delete" button and bugs will be deleted.
Once done the changes its always safer to turn the allowbugdeletion parameter off to avoid accidental deletions.