Customers wait in line to buy the new iPhone 4S at Apple's retail store in downtown Shanghai, Jan 13, 2012. [File Photo]

Apple Inc's revenue growth rate in China, its second-biggest regional market, was double its global level in the second quarter of this year, though it posted less-than-expected revenue, the world's No. 1 tech firm revealed Wednesday.

Apple's revenue in China, which accounts for 20 percent of its global income, posted a growth rate of 48 percent year on year in the April-June quarter, compared with a 23 percent growth globally.

Sales of iPhone jumped 100 percent year on year in China in the quarter after Apple, in partnership with China Unicom and China Telecom, launched the latest iPhone 4S in the country in the first quarter.

Apple's China revenue hit US$5.7 billion in Q2.

Though revenue decreased from the first quarter for seasonal reasons, Tim Cook, Apple's chief executive, commended the growth in China, calling it an "incredible rate."

In the first quarter when Apple launched the iPhone 4S, Apple's revenue in the country hit a record US$7.9 billion, up 94 percent from a year ago.

Sales of iPhone will continue to surge thanks to Apple's likely cooperation with China Mobile, the world's biggest mobile carrier by subscriber base.

Sales of iPad are also expected to grow after Apple settled a long-term trademark dispute and finally officially launched the latest iPad on the Chinese mainland last week, industry insiders said.

At the start of this month, Apple agreed to pay US$60 million to Shenzhen-based Proview to settle their dispute.