Apple has confirmed it is working to fix an issue that is preventing some iPhones from playing the alarm sound.

Users around the globe have been taking to social media over the last 24 hours complaining that they overslept because their phone alarm failed to sound and wake them.

Apple has said it is aware of the issue and is working to fix it.

Some iPhone owners have suggested the problem could be connected to the device’s Attention Aware setting, which when active can cause the phone to lower the volume of some alerts and sounds because it senses a face near to the screen which it perceives to be using it.

It remains unclear how many phones could be affected or whether the problem is connected to a particular phone model or specific version of its IOS software.

Until the issue is resolved users are also being encouraged to check all alarm settings and volume limits before going to bed or needing to set an alert to ensure the phone is operating at the correct volume.