Unlike last year, Apple didn’t give figures for preorders in the first 24 hours. The new models, introduced at an event in San Francisco last week, feature an improved camera, faster processor and a new feature called 3D Touch that provides shortcuts to common tasks when pressing firmly on the screen.

"Customer response to iPhone 6s and iPhone 6s Plus has been extremely positive and preorders this weekend were very strong around the world," Apple spokeswoman Trudy Muller said.

Maintaining healthy demand for the iPhone is critical for Apple, which got more than 60 percent of its revenue from the handsets in recent quarters.

Analysts also have raised questions of whether the new models will be able to match the success of last year’s record-setting release, when the company overhauled the design of the device with bigger screens.

In September 2014, the phone maker got a record number of first day preorders of the iPhone 6 and iPhone 6 Plus, with more than four million in the first 24 hours.

The stock has fallen 13 percent since July 21, when Apple released financial results that were lower than analysts anticipated, leading to concerns the company can keep up its strong growth year after year. An economic slowdown in China, a key market for Apple, has added to the investor hand wringing.

The new iPhones hit stores Sept. 25 in Australia, Canada, China, France, Germany, Hong Kong, Japan, New Zealand, Puerto Rico, Singapore, the U.K and the U.S. The company also started a new leasing program where customers can get a new iPhone every year starting at $32 per month.