Shipments of fitness trackers and smartwatches surged in the third quarter, research firm International Data Corp. said in a recent report.

Fitbit remains the leader in the global wearable market despite increased competition from Apple and Chinese companies, according to data from IDC's Worldwide Quarterly Wearable Device Tracker, which were released Thursday.

Compared to Fitbit's 22 percent market share, Apple came in at No. 2 with 18.6 percent in its second quarter after introducing the Apple Watch. Not trailing far behind was Chinese vendor Xiaomi, which grabbed 17.4 percent of the market.

"China has quickly emerged as the fastest-growing wearables market, attracting companies eager to compete on price and feature sets," wrote Ramon Llamas, research manager for IDC's wearables team, in the report. "The challenge, however, is whether these vendors can expand their presence, as few have extended beyond the country's borders and into other markets."

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Wearable shipments have nearly tripled since 2014, with 21 million units shipped in the third quarter compared to 7.1 million in the same quarter last year, according to IDC. Korean tech giant Samsung was missing from IDC's rankings of the top five wearable vendors. A Chinese firm, BBK, beat out Samsung for the fifth spot with a single product — a smartwatch made for children that only sells in China.

Samsung did not immediately respond to CNBC's request for comment.