Serbia is country code +381.
You must drop the trunk prefix '0' from the beginning of the Serbian number when calling from other countries. For example, Belgrade's area code 011 becomes +381 11.
Mobile numbers begin with +381 6.
Mobile numbers in the disputed region of Kosovo begin with +377 44, +377 45, +386 43, or +386 49. (Country code +377 is Monaco; country code +386 is Slovenia.)
The country code and area code of Bor, Serbia is 381, (0)30.
The country code and area code of Beograd, Serbia is 381, (0)11.
The country code and area code of Cacak, Serbia is 381, (0)32.
The country code and area code of Dakovica, Serbia is 381, (0)390.
The country code and area code of Jagodina, Serbia is 381, (0)35.
The country code and area code of Kikinda, Serbia is 381, (0)230.
The country code and area code of Kragujevac, Serbia is 381, (0)34.
The country code and area code of Krajevo, Serbia is 381, (0)36.
The country code and area code of Krusevac, Serbia is 381, (0)37.
The country code and area code of Leskovac, Serbia is 381, (0)16.
The country code and area code of Pancevo, Serbia is 381, (0)13.
The country code and area code of Pec, Serbia is 381, (0)39.