Amazon shares have surged more than 18% in after-hours trading after it reported a surprise profit and better-than-expected sales figures, according to BBC News.

The online retail giant reported a $92mln profit compared to a $126mln loss for the same period a year ago. Sales also rose 20% to $23.2bn in the second quarter to the end of June, boosted by strong growth in the U.S.

Its shares, which fell 1.3% during the day, leapt 18.5% to $571.24 a share in after-hours trading on Wall Street.

The firm was also upbeat on its prospects for the current third quarter, forecasting sales would grow between 13% and 24% compared to last year, much higher than analysts had predicted.

Sales in North America rose 25.5% to $13.8bn in the second quarter, driven by purchases of electronic goods and general merchandise, helping to drive the strong performance.

Its cloud computing division, Amazon Web Services, also made a contribution, with sales up 81% compared to the same quarter last year.

It said its widely promoted "Prime Day" on July 15 - which offered special deals to customers who signed up to its fast delivery service - had been a success with more new members trying it globally than any other day in the firm's history.

Amazon founder and chief executive Jeff Bezos credited hard work for the results. "The teams at Amazon have been working hard for customers," he said.