Apple has apologised after an update to its mobile operating system left some owners of its new iPhones unable to make or receive calls.
Users who had installed iOS 8.0.1 on the iPhone 6 models also complained it had caused problems for the handsets' Touch ID fingerprint facility.
The update had been released less than a week after the phones had gone on sale in order to fix other issues.
Apple said it was working on a new version.
"We have a workaround for iPhone 6 and iPhone 6 Plus users who lost cellular service and Touch ID functionality today after updating to iOS 8.0.1," it said.
"Affected users can reinstall iOS 8 through iTunes.
"We apologise for the great inconvenience experienced by users, and are working around the clock to prepare iOS 8.0.2 with a fix for the issue, and will release it as soon as it is ready in the next few days."
The company has also published a support document that lists the steps affected users can take to revert their devices to the previous version of the operating system.
The iOS 8.0.1 update had been made available online for less than an hour before it was pulled on Wednesday.
MacRumors reported that within that time it had caused connectivity problems for subscribers to networks including EE in the UK, Vodafone in Germany, AT&T and Verizon in the US and Rogers in Canada.
Apple had said the update was intended to fix other bugs including:
- An issue that could cause unexpected data usage when receiving a text message
- A bug that had prevented apps designed to work with its HealthKit software from being made available
- An issue that prevented some apps from accessing photos on the iPhone or iPad's library
While it is common for tech companies to issue bug fixes shortly after the release of a major new version of software, it is not usual for them to have to recall the code.
The mistake comes at a time when Apple has suffered a series of setbacks.
Last week it released a tool to remove the new U2 album from iTunes users' libraries - which it had given away for free - after complaints that its songs had automatically been downloaded to devices without their owners' permission.
On Tuesday, claims were made that some of the new iPhones had bent after being placed in users' pockets - it is as yet unclear whether this is a major problem or not.
And on Wednesday, it emerged that a bug in OS X could leave the company's Mac computers open to attack.
The Shellshock bug also affects computers powered by Linux.