Analysis from research firm Canalys has claimed that Apple has shipped 4.2 million units of the Apple Watch, despite the device's high retail price, and is now leading the wearables market.
Canalys said that Apple took the top spot in the market during the second quarter of 2015, "easily" overtaking more established companies like Fitbit and Xiaomi.
These are early stages for the market, and the analysts said that Apple and its rivals need to boost performance, app availability and battery power.
The Apple Watch is described as being "significantly" more expensive, but has made its mark through an "excellent" software developer kit and a passionate user base.
Canalys added that shipments would have been higher if Apple had released the Watch earlier and had the stock to meet demand at the launch.
"The Apple Watch is the most sophisticated smartwatch to date, and it has proved popular with Apple fans worldwide," said Chris Jones, vice president and principal analyst at Canalys.
"But Apple and other vendors still face important challenges to make the smartwatch a breakout hit.
"Improvements in performance, battery life and sensor integration are needed to make future models more attractive, but it is the quality of third-party apps that will determine whether the Apple Watch will be a long-term success."
The Apple Watch was pitched for success in the wearables market before it was released, and the firm has made it available in a number of geographies and options.
It has a starting price of £299, rising to over £10,000. V3's review of the mid-range Apple Watch found the device expensive but well designed and strong on performance.
V3 has asked Apple for its comments on shipments so far, but the company has typically declined to reply.
The firm is due to announce its third-quarter results today, which are expected to include figures for Apple Watch sales so far.
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