Amazon profits fell in its third quarter but shares in the business soared as it beat market expectations.

The US etail titan posted a 40% slump in operating income to $347m in its third quarter, ending September 30.

The total included a $21m profit contribution from Whole Food Market, which it acquired at the end of August.

Net income edged up 1.6% to $256m during the period, as net sales soared 34% to $43.7bn.

Whole Foods contributed $1.3bn to Amazon’s sales total, while the online Goliath also benefited from a $124m “favourable impact” in exchange rate fluctuations.

Amazon said net sales were up 29% after stripping out the impact of Whole Foods and currency changes.

Shares in the business were up more than 7% in the hours after trading in the US yesterday.

Amazon boss Jeff Bezos said the number of active customers using Alexa-enabled voice-activated devices were up five-fold compared to the same time last year.

It introduced three new Echo devices during the period as demand for voice-enabled shopping continues to grow.

As well as investing in technology, Amazon opened four new bookstores during the quarter, including a second site in New York and two in California.

The etailer now has 12 bookstores across the US, with further openings planned in Washington DC, Walnut Creek in California and Austin, Texas.