Amazon has launched an online grocery division selling 22,000 products, putting pressure on online grocery specialist Ocado, which is gearing up for an initial public offering in the UK.

It will reportedly offer a wider range of products than Ocado, including brands such as Pampers nappies, Ariel washing powder and Pedigree Chum dog food.

Amazon - best known for its online books/CD sales - said that products from the big consumer goods firms such as Kraft, Nestlé and P&G would be on offer at its online grocery store. It added that an undisclosed number of its products will be provided by third-party members of its Amazon Marketplace.

Ocado had announced on Tuesday that it is aiming for a market valuation of £1.37bn in an initial public offering later this month, which some analysts consider too high. The retailer sells 20,000 products, about a quarter of which come from Waitrose.

Founded in 1995, Amazon had global sales of $24.5bn (£16bn) last year.