wp-admin and htaccess issue

I’m trying to implement htaccess in wp-admin, but having issues. wp-login.php looks broken and when I try to login I’m sent to 404 page error. Here’s what I use as per resource from WP Codex page.

AuthUserFile /path/to/.htpasswd
AuthType basic
AuthName "Restricted Resource"
require valid-user

<Files admin-ajax.php>
    Order allow,deny
    Allow from all
    Satisfy any
</Files>

htaccess is placed in wp-admin folder. Not sure what I’m missing.

Thanks.