Apple’s co-founder Steve Jobs made a surprise appearance to launch iPad 2, the updated version of its original iPad tablet computer which was released last year in January at the same venue and by the same man.

Jobs launched the new device at an event at the Yerba Buena Center for the Arts Theater in San Francisco on 2 March.

There was speculation whether Jobs will attend the event or not. Jobs has been on an indefinite medical leave from mid-January this year.

Apple’s iPad 2 is thinner, faster and slightly lighter than the original. It features two cameras, the front one meant for video conferencing. The tablet computer runs on the new dual core A5 processor and for the first time, will be available in white, apart from the standard black. The iPad 2 will also have Apple’s latest operating system, iOS 4.3.

Apple has not changed the pricing of the device, with models starting at $499. The company says iPad 2 will hit the stores in the US from 11 March and from 25 March in the UK and other countries.

The launch also puts the new iPad on an annual cycle of updates that are similar to those of the iPhone and iPod media player.

However, the event was focused on the unexpected reappearance of Steve Jobs.

Presenting the updated device to a packed conference centre, Jobs said he did not want to miss the launch.

He said, "We’ve been working on this product for a while, and I didn’t want to miss it. Thank you for having me."

Jobs said 100 million e-books were downloaded since the company’s bookstore was introduced a year ago. He added that publisher Random House would be on its bookstore which is expected to bring 17,000 more publications.

He said the iTunes Store is now the biggest credit card account holder on the Internet with 200 million accounts worldwide.

He added, "We’ve sold 15m iPads in nine months, that’s more than every tablet PC ever sold."

"We got over 90% market share. Our competitors were flummoxed."

Jobs also showed a new thin iPad cover that uses magnets to attach to the device, turns it on and off, and also doubles as a stand.