China Unicom (CHU), the second largest carrier in the world’s largest mobile phone market, received a government permit this week to begin selling the iPhone 4S on mainland China this month, according to two Chinese-based news outlets (see here and here).

However a third source, citing a report by unnamed China Unicom “insiders” to Sina Tech, says the permit issued was for the iPhone 4, not the 4S. See here.

Greater China — which Apple (AAPL) defines as Hong Kong, mainland China and Taiwan — is the company’s fastest-growing market, with sales up 270% since 2010, thanks in large part to the seemingly unquenchable appetite for iPhones among China’s growing middle class.

When Apple began taking pre-orders the iPhone 4S in Hong Kong last month, they sold out in 10 minutes (see here). A week later, when the phone went on sale, riot police had to be called in to control the line-cutters and scalpers snapping up iPhones for re-sale at steep mark-ups on the mainland. (See Massive crowds gather in Hong Kong for iPhone 4S launch.)