One user said Apple had helped him to replace his faulty Duo unit
Apple says it will replace iPhone Duo handsets that have developed problems with their screens just days after the highly-anticipated smartphone went on sale.
Photos posted by social media users show lines that appeared on the screens of the technology giant's first ever foldable device, which has a starting price of £1,999 ($2,668) in the UK.
Apple said it is aware of "an issue impacting the inner display on a small number" of units and urged affected users to contact the company for a replacement.
The Duo's launch, which attracted long queues at Apple stores around the world last week, comes as the brand tries to reinvigorate its catalogue and challenge the foldable phones offered by rivals.