Fitbit shares tumble as Apple watch gains market share

Shares of Fitbit, the maker of popular fitness tracking devices, sank 18 per cent on Tuesday as investors worried about its ability to compete with Apple and other makers of wearable technology.

The sudden stock drop was hardly in line with the company's hopes going into this week's consumer electronics show, the International CES, in Las Vegas. Earlier on Tuesday, Fitbit introduced the Fitbit Blaze, a fitness watch priced at $US200, which will be available in March.