WASHINGTON (AFP) - Strong holiday season sales of Apple's newest smartwatch propelled the tech giant into the lead in wearable tech in 2017, a market tracker said on Thursday.

A report by the research firm IDC said Apple jumped to the front of the wearables pack in the fourth quarter following the release of Apple Watch 3.

While official sales figures are not disclosed, IDC estimated Apple sold some eight million in the final three months of last year, representing 21 per cent of all wearables.

That pushed Apple ahead of US rival Fitbit which had a 14.2 per cent share of wearables in the quarter, and China's Xiaomi (13 per cent).

"Interest in smartwatches continues to grow and Apple is well-positioned to capture demand," said IDC research director Ramon Llamas.

"User tastes have become more sophisticated over the past several quarters and Apple pounced on the demand for cellular connectivity and streaming multimedia."

For the entire 2017, Apple sold an estimated 17.7 million smartwatches, accounting for 15.3 per cent of the wearable tech market, according to IDC.

That was ahead of Xiaomi (13.6 per cent) and Fitbit (13.3 per cent) for the full year.

IDC said the overall wearables market - which includes fitness trackers, smart clothing, eyewear and other devices - rose 10.3 per cent in 2017 to 115.4 million units. That compared with a sharper 27 per cent increase in 2016.

"The slowdown is not due to a lack of interest - far from it," Mr Llamas said.

"Instead, we saw numerous vendors, relying on older models, exit the market altogether. At the same time, the remaining vendors - including multiple start-ups - have not only replaced them, but also with devices, features and services that have helped make wearables more integral in people's lives."