Online retailer Amazon has reported first quarter sales up 37 per cent to US$4.1 billion (£2.08 billion), but warned that changes in global economic conditions could affect profit margins this year.

For the first quarter to March 31, 2008, net income rose 30 per cent to US$143 million (£72.5 million), compared with a net income of US$111 million (£56.3 million) in the first quarter of 2007.

“Our sales growth this quarter was driven by low prices and millions of in-stock items available for immediate shipment,” said Amazon founder and chief executive officer Jeff Bezos.

International sales, covering the UK, German, Japanese, French and Chinese sites, were US$2.01 billion (£1.01 billion), up 44 per cent on the first quarter 2007. International sales now represent 49 per cent of worldwide net sales compared with 46 per cent the previous year.

Amazon said net sales are expected to be between US$3.88 billion and US$4.08 billion (£1.97 billion and£2.07 billion) or grow between 34 per cent and 41 per cent in the second quarter of 2008.

It said results could be affected by factors such as fluctuations in foreign exchange rates, changes in global economic conditions and consumer spending.