The Apple Watch's share of the global wearables market is on the rise, but still leaving the company behind rivals Xiaomi and Fitbit, according to research data published this week.

Apple shipped an estimated 2.8 million Watches in the June quarter, representing 13 percent marketshare, Strategy Analytics said. The exact figure is unknown, as Apple didn't break out Watch numbers in its quarterly results except to say sales were up 50 percent, and that it has the top-selling smartwatch in the world. A year ago Apple is thought to have shipped about 1.8 million units, putting it at 9 percent share.

The reigning wearables company is currently Xiaomi — which thanks to its low-cost Mi Band fitness trackers shipped 3.7 million units in the June quarter, up from 3 million a year ago. The company's marketshare rose from 15 to 17.1 percent.

Taking a blow was Fitbit, which saw its share plummet from an industry-leading 28.5 percent to second-place 15.7, as shipments slid from 5.7 million units to 3.4.

"Fitbit is at risk of being trapped in a pincer movement between the low-end fitnessbands sold by Xiaomi and the fitness-led, high-end smartwatches sold by Apple," wrote Strategy Analytics executive director Neil Mawston. Much of the company's future may hinge on its first smartwatch, due by the end of the year.

The wearables industry as a whole reportedly grew 8 percent, a slower pace than the 21.2 percent seen in Q2 2016.