I'm no expert but in theory this should be achievable through your .htaccess file. All you would need to do is deny access to the IP address list associated with this country e.g.
deny from 18.104.22.168/12
deny from ......etc
There are a few website out there that you can use to source these address lists although they are subject to change so I guess you'd need to keep updating .htaccess
You could then customise an error 403 document (if you're using an apache server anyway) and bingo all sorted.