Where can I find who is responsible for domain name registration in my area?

For generic TLD's (.com/.net/.org) contact a gTLD registrar.
http://www.icann.org/registrars/accreditation-qualified-list.html

For country code TLD's (where 'area' = 'country') see
http://www.iana.org/cctld/cctld-whois.htm