Amazon reported that it had once again surpassed its retail rivals in the last quarter, with sales going up by thirty six percent.

But shares of the largest online retailer of the world declined by eight and a half per cent in later part of trade on woes that its profit margins could fall as it expands its business. In comparison of that, shares of Borders, a traditional bookstore chain, went up by thirty four per cent in after-hours trade following its announcement of new financing.

For the on going quarter, Amazon forecast that its net sales would go up ranging between twenty eight and thirty nine per cent against a year ago, to between $9.1bn and $9.9bn.

The firm stated that it expected its operating income to fall to between two hundred and sixty million dollars and three hundred and eighty five million dollars including one hundred and forty million dollars of charges for stock-based compensation and suspension of intangible assets.

For the forecast its shares saw a decline of more than ten per cent in after-hours trading to hit one hundred and sixty dollars and fifty cents as investors responded to a potential decline in operating profit margin, which has been an issue for investors, worried about Amazon's preparedness in spending for developing new technology.

In the final quarter sales of North America the firm saw a rise of forty five per cent, encouraged by Amazon's $1.2bn purchase of Zappos, the online shoe and accessory business. The strong growth tallies with estimated overall US online sales growth of about sixteen per cent for November and December.

Amazon's international business of Amazon in countries like Japan, UK, China, Germany, France and Italy saw revenues growth of twenty six percent at $5.74bn against the same period of the earlier year. Net earnings increased eight per cent against a year ago to $416m, or ninety one cents per diluted share.