Early adopters of the Apple Watch, Apple's first new product in five years, are complaining that a number of its key functions are disrupted by their tattoos.

Owners of Apple Watch have found that their inked skin confuses the sensors on the underside of the device.

Users of the watch, which went on sale last week, took to social media under the hashtag #tattoogate to air their frustration with the flaw from Apple's renowned design house.

One user on Reddit, an entertainment, social networking, and user-generated news website, said the device's locking mechanism, which should disengage when the watch detects it is being worn, failed to work on decorated skin.

"My hand isn't tattooed and the Watch stayed unlocked. Once I put it back on the area that is tattooed with black ink, the watch would automatically lock again," the user wrote.

A website support page from the company says tattoos can interfere with readings from the heart rate monitor, but does not mention interference with other functions.

"Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings," it said.

The tattoo issue follows a report in the Wall Street Journal that some taptic engines, which produce the sensation of being tapped on the wrist, started to break down over time, a flaw that was slowing the rollout of the item.