The iPhone Duo has drawn numerous complaints from users who said its foldable screen cracked after just hours or, in some cases, days of use.

Multiple users complained of hearing a crunch when unfolding the phone, while others noticed white patches around the crease on the screen, indicating a malfunction.

Bloomberg News verified the reports from more than half a dozen people whose foldable iPhones had developed faults.

Apple released the iPhone Duo, its first foldable phone, earlier this year, joining manufacturers such as Samsung and Huawei, which have made similar devices for years.

Apple acknowledged the problem in a statement, saying it was “aware of an issue impacting the inner display on a small number of iPhone Duo units”.

The company directed affected users to contact its customer care centre for replacements.

“If users experience issues with their iPhone Duo display, they should contact AppleCare for a replacement,” Apple said.

Tom Battle, an Apple user from San Diego, told Bloomberg that his phone had become harder to open and that, when it eventually opened, lines appeared on the screen.

“I went to unfold it and it felt stuck/harder/slower to open than usual. And when I opened it it had the lines on the screen,” Mr Battle told Bloomberg. “You could feel a bump or loose piece under the display.”

Another user, Centrino31A, told Bloomberg that he had experienced a similar issue, noting that the outer screen worked perfectly.

“I was reading Apple News and decided to open the display to enjoy it, and that’s when I saw the crack line and bruising,” Centrino31A told Bloomberg. “There is no damage to the outside of the phone nor to the inner display surface. It is pristine. The issue is the underlying display.”

“Bloomberg didn’t encounter the issue on one review unit provided by Apple or another device purchased independently,” the paper reported.