Amazon has started sending out invites to a press conference that has sparked repeated rumours that the company is about to show off some new versions of its Kindle ebook readers.

The company has been expected to announce some new products for a while, and the August-September timeframe is its usual announcement zone in order to get sales during the end-of-year holiday season.

Amazon is thought to be working on two new Kindle Fire tablets - an upgrade to the existing 7-inch model and a new 10-inch model to take it firmly into the mainstream tablet market.

The press conference is being held on the 6th September, just after Nokia's announcement, and a week before Apple's.