Online giant Amazon said second quarter group sales surged 51% to $9.91bn but net income fell in the period.

The US etailer reported net income decreased 8% to $191m as it continued to invest in opportunities. It acquired UK online book store the Book Depository in the period and is opening new distribution centres to fuel growth.

International sales - which comprises the UK, as well as Germany, Japan, France, China and Italy sites – rocketed 51% to $4.51bn. founder and chief executive Jeff Bezos said:  “Low prices, expanding selection, fast delivery and innovation are driving the fastest growth we’ve seen in over a decade.”

Bezos said the Kindle 3G with Special Offers has “quickly become our bestselling Kindle at only $139. Customers love the convenience of a 3G reader”.

Net sales for the third quarter are expected to be between $10.3bn and $11.1bn.