Amazon said that profits more than tripled in the second quarter — usually a quiet period for retailers — in a sign that years of heavy investment in technology could finally be delivering results.

The largest online retailer also raised full-year revenue and profits forecasts as it posted profits of $78 million (£38m) for the three months to June. Sales were up 35 per cent, at $2.9 billion. Both figures beat analysts expectations.

The group was also boosted by 2.2 million pre-orders for the final instalment of the Harry Potter series of novels, Harry Potter and the Deathly Hallows, in what was Amazon’s largest ever product launch.

Worldwide, revenue from electronics and general merchandise improved 55 per cent to $970 million, while sales of books, music and other media-category products grew 27 per cent to $1.83 billion.

The retailer added that a weaker dollar had helped sales.

It said that technology spending in the quarter rose 20 per cent year-on-year, down from nearly 60 per cent a year earlier.

Amazon upped its revenue forecast for the full fiscal year to $13.80 billion to $14.30 billion, up from its earlier outlook for $13.4 billion to $14 billion.

Wall Street is currently looking for full-year sales of $13.84 billion and third-quarter revenue to reach $3 billion.

For the current third quarter, Amazon said it expects revenue from $3 billion to $3.18 billion.

Shares in Amazon soared $14.70, or 21 per cent, to $83.95, in after-hours electronic trading in New York following the earnings statement.

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