
Worldwide pre-orders for the new smartphone were "very strong" and "on pace to beat last year's 10 million unit first weekend record" set by the then-new iPhone 6, Apple said in a statement.
Apple said the online demand exceeded its own forecasts.
The iPhone is by far Apple's biggest earner, pulling in more than 60 per cent of the company's annual revenue. In March, chief executive Tim Cook announced the company had sold 700 million of the smartphones since their launch in 2007.
The latest iPhone model features new pressure-sensitive touch-screen technology and new "peek and pop" content preview functions.
Apple introduced the iPhone 6s at a launch in San Francisco on September 9, and it will go on sale worldwide September 25.