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Fitbit the maker of wearable activity monitors, tripled its third quarter sales - capitalising on the popularity of wearable fitness technology.

The company brought in $409.3m (£265.5m) in the third quarter compared to $152.9m in the same period the year before.

Fitbit sold 4.8 million devices between July and September compared with 2.3 million in the third quarter of 2014.

The company said it saw "tremendous opportunity" to grow.

"Fitbit's third quarter results demonstrated the continued rapid growth of the Fitbit platform and our team's ability to execute on the tremendous opportunity we see globally," said chief executive James Park.

Despite the growth, the company's net income fell to $45.8m from $68.9m due to rising costs.

Fitbit sold shares for the first time on the New York Stock Exchange in June and today the company said it would sell more shares on 4 November.

In after-hours trading Fitbit shares tumbled 7%.