Days after the launch in Beijing, both of Apple's current Chinese carriers will accept pre-orders. It will take about a week for them to deliver the new iPhones to their customers, the source said.

News of the iPhone debuts leaked on Sina Corp's Weibo microblog, which briefly carried a pre-order advertisement for the latest models on China Telecom's verified page in Beijing. The post was quickly taken down, although word had already spread among bloggers, many of whom posted screenshots of the announcement.

"Have you prepared your cash to welcome the iPhone 5S and 5C? I'm looking forward to it," said a Sina microblogger.

Over the past few quarters, Apple's China market share has dwindled due to stiff competition from global rivals like Samsung Electronics Co Ltd and domestic players selling phones that cost a fraction of the iPhone.

Its second-quarter market share slipped to 5 percent and was ranked No.7, trailing Samsung, Lenovo Group Ltd, Yulong Computer, ZTE Corp, Huawei Technologies Co Ltd and Xiaomi, according to research firm Canalys. Apple's iPhones had a market share of 8 percent, making it the No 5 vendor, in the first quarter, Canalys said.

"It's a very good direction that Apple is launching its latest model so soon in China when its brand attraction is on the decline," said Nicole Peng, an analyst at Canalys. "It is a sign that they value the Chinese consumers."

In another sign that its Chinese sales were faltering, Apple's greater China revenue for its fiscal quarter ending June plunged 43 percent from the previous period and 14 percent from the same quarter last year to around $5 billion.