The latest iTunes Producer Guide, version 2.8, says that a number of new languages are now supported by iBooks and the iBookstore using the ePub 3 format. iBooks 3 and iOS 6 are required. These are:
Arabic, Burmese, Chinese, Dari, Hebrew, Japanese, Khmer, Kurdish, Lao, Malay, Pashto, Persian, Punjabi, Sindhi, Tajik, Urdu, Uyghur, and Uzbek
Some info regarding producing epub3 can be found at
Hindi has always been supported while Urdu is new. That may make a difference.
I'm curious how you could make a book in Urdu with iBA, because it is usually too buggy for Arabic script to be usable.