Amazon has revealed that it has sold about 1 million Kindle ereaders and tablets a week over the past three weeks, the first time it has given any detailed indication of sales of its new product line.

While it did not break out separate numbers for the Kindle ereader and its new Kindle Fire tablet, it said that Kindle Fire sales have risen week-over-week for the past three weeks. According to Bloomberg, the Kindle Fire has been the best-selling product on Amazon.com since its introduction 11 weeks ago.

The Android-based tablet – available in the US for US$199 – is considered a major rival to Apple’s iPad, retailing at less than half the price of the cheapest Apple tablet.

"They have not talked about numbers at all, so it’s a big deal that they for some reason think they need to disclose metrics now,” Brian Blair, an analyst at Wedge Partners, told Bloomberg. “It’s a part of their strategy to show the strength of it against Apple — a way to say, ‘we’re a player, and we’re going to start letting you know.’”

Amazon has raised production of the tablet two or three times since its introduction and will probably sell 5 million to 6 million Kindle Fires by the end of the year, Blair said.

The firm is expected to post a loss in the fourth quarter as it ramps up spending on its new line. According to Bloomberg, Amazon’s operating margin may narrow to 0.79 percent this quarter from 3.66 percent a year ago.