The Apple Watch is not working properly for some users - and it is because of their tattoos.

Early buyers of the iPhone maker's first smartwatch, which can cost up to £13,500, have taken to social media to report issues with some of their device's features when placed on wrists decorated with tattoos.

Dark ink is said to disrupt and confuse some of the sensors in the underside of the device that track when the watch is being worn, and also to monitor heart rate.

An article on the support page of Apple's website has confirmed that this can be an issue for tattooed wearers of the watch.

"Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance," Apple said.

"The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings."

The support page explains that the watch uses green LED lights combined with light-sensitive photodiode sensors to detect the amount of blood flowing through the wrist, which can then be used to calculate heart rate.

Detecting the skin also helps the watch establish when it is being worn; and automatically unlocking when a wearer lifts their wrist to check the device.

Some users have been reporting the screen staying locked when raising a tattooed wrist.

Videos posted to YouTube have also shown users with wrist tattoos attempting to log a work out session, only for the Watch to intermittently pause the stopwatch when it failed to detect the wrist.

The news follows a report by the Wall Street Journal that the taptic engine within the watch that creates the vibrations mimicking being tapped on the wrist - used for notifications - break down over time and are leading to a slowing of production rate.

But when Luca Maestri, Apple's chief financial officer was asked by the Financial Times how the watch's early sales compared to the launch of the iPhone and iPad, he said they were "very good compared to that".

The iPhone sold 270,000 units on its first day back in 2007, while the iPad sold 300,000 units on day one in 2010.