Owners of Apple's new foldable iPhone are reporting cracks in the device's screen, and the company has confirmed a problem affecting a "small number" of units. The handset, called the iPhone Duo, is Apple's first foldable phone and retails from $1,999 (£1,499).

Reports have appeared on Reddit and other social media platforms since the phone went on general sale worldwide on Friday. Experts said there were too few examples so far to say whether the issue points to a wider flaw in the device.

In a statement, Apple said: "We are aware of an issue impacting the inner display on a small number of iPhone Duo units. If users experience issues with their iPhone Duo display, they should contact AppleCare for a replacement." The company believes the affected units show defects soon after use, and said early user feedback had been "incredibly positive".

One user in Australia wrote on Reddit that their Duo cracked within six hours of being collected. They said they felt something near the internal hinge, beneath the screen, while showing the phone to a friend. "As I continued opening it, I heard an audible crack, and the screen broke right along the hinge," they wrote. They shared an image showing a white strip of light running along one half of the display. The user said their local Apple store replaced the phone immediately. The Guardian has been unable to verify the claims.

A second Australian user posted that they had heard "almost a cracking noise" from their handset, followed by a similar screen malfunction. Bloomberg also reported comparable problems among users in the US and India.

The Duo is the most high-profile launch under Apple's new chief executive, John Ternus, who succeeded Tim Cook in September. Apple said demand had been "nothing short of extraordinary". According to the Economic Daily, a Taiwan-based publication, the device has sold out and the next round of shipments is not expected until January. Taiwan is the home country of Foxconn, Apple's main device manufacturer.

Francisco Jeronimo, vice-president of data and analytics at the research firm IDC, said it was too early to tell whether the screen issue was significant. "This is quite common when a new product comes to market," he said. He pointed to Samsung's difficulties with the original Galaxy Fold in 2019, saying that episode showed a fast and transparent response can limit damage to a product category. In his view, Apple's advice that affected customers ask for a replacement is "the right first step".

Ben Wood, chief analyst at the research firm CCS, said he was taking a very cautious view of the problem. He added that there was so far no evidence of a more widespread issue with the device.