European Competition Commissioner Margrethe Vestager made the statement a week after launching an investigation into the US. online retailer's ebook deals with publishers.

Vestager announced last week she would examine whether clauses in Amazon's contracts prevent publishers from offering more favourable deals to competitors.

Ebooks are a fast-growing industry and Amazon, which popularized the product, is Europe's biggest player. However, it should not abuse its market dominance, Vestager said.

"Amazon should not use its strong position to close the door behind it and prevent companies with new ideas from contesting the market," she told a conference.

The company could be fined up to 10 percent of its global turnover if found guilty of breaching EU rules.

Amazon is not exactly the EU's favourite company. It is also being investigated for its deals with Luxembourg which allow it to pay extremely low taxes.

The EU competition authority is investigating whether the case gives Amazon an unfair advantage.