Registration spam

Two days ago I started to get a lot of spam registrations. I have reCAPTCHA on the registration form.
Any suggestion on what to do more to eliminate spammers?
I have in mind to add an extra field that users need to fill in with the specific word that will know only people from my country, but I, can't find that feature and how to add it?
Any other better solution?
Thank you

I looks like it's not going to work in combination with RO Payments.