User Registrations although registrations are disabled ?

I have disabled registrations in the WordPress admin interface and deleted the wp-register.php file as well. Even though I did that I still receive 1-2 registrations per day which are obviously spam registrations by bots. (using a .ru mail address)

I would like to know how someone can still register an user even though I have disabled that option in WordPress. More pressing than the how is a way to stop registration once and forever.