Apple became the world's largest wearables vendor in the first quarter of 2017 with an estimated 3.5 million Apple Watch shipments, according to new research data shared this afternoon by Strategy Analytics.

Apple Watch shipments overtook Fitbit shipments during Q1 2017, allowing Apple to capture 15.9 percent global marketshare to become the top wearables vendor. Fitbit shipped an estimated 2.9 million wearable devices during the quarter, while Apple's closest competitor, Xiaomi, shipped an estimated 3.4 million wearable devices.

Apple's estimated 3.5 million shipments are up from an estimated 2.2 million Apple Watch shipments in the year-ago quarter. As Apple Watch shipments have grown, Fitbit shipments have dropped sharply from an estimated 4.5 million units in Q1 2016.

Cliff Raskind, Director at Strategy Analytics, said, "Fitbit shipped 2.9 million wearables worldwide in Q1 2017, falling a huge 36 percent annually from 4.5 million in Q1 2016. Fitbit has lost its wearables leadership to Apple, due to slowing demand for its fitnessbands and a late entry to the emerging smartwatch market. Fitbit's shipments, revenue, pricing and profit are all shrinking at the moment and the company has a major fight on its hands to recover this year."

Xiaomi is still close to Apple at 15.5 percent global marketshare, but has seen its shipment numbers slip while Apple's have grown.In the year-ago quarter, Xiaomi's marketshare was at 20.9 percent, while Apple's was at 12.1 percent. Fitbit, meanwhile, has dropped from 24.7 percent in Q1 2016 to 13.2 percent in Q1 2017.

Apple does not share official Apple Watch sales numbers, instead lumping the device into its "Other Products" category that also includes the Apple TV, Beats products, iPod, and Apple-branded and third-party accessories, so Apple Watch sales numbers shared by various analytics firms are all estimates.

Revenue from "Other Products" was $2.87 billion during the second quarter of 2017 according to Apple's recently released earnings report, up from $2.19 in the year-ago quarter. According to Apple CEO Tim Cook, Apple Watch sales have nearly doubled year-over-year.

"Combine Apple Watch, AirPods, and Beats and our revenue from wearable products in the last four quarters was the size of a Fortune 500 company," said Cook.

Update: According to Fitbit, which does publish its sales numbers, 3 million Fitbits were sold during 1Q 2017, not 2.9 million.