Amazon's shares fell in after-hours electronic trading in New York, indicating that they will start $3.37 lower when markets open on Wednesday.

Analysts questioned the company's strategy of focusing on its discount shipping programme, Amazon Prime, at a time when it was facing intense competition and having to increase spending on technology.

Martin Pyykkonen, an analyst at Global Crown Capital, said that Amazon did not seem to be stimulating sales growth in the way many had hoped.

"Although Amazon Prime may be having some shipping impact, it's not a windfall for the company," Mr Pyykkonen said.