Apple chief executive Steve Jobs emerged from medical leave on Wednesday to unveil a new version of the iPad designed to tighten the company's grip on the booming tablet computer market.

The iPad 2 is thinner and lighter than the original version released last year and features cameras for photography, movie-making or video chat.

"We've been working on this product quite awhile and I just didn't want to miss a great day," said Jobs, who appeared gaunt but energetic and was dressed in his trademark long-sleeve black turtleneck and blue jeans.

Jobs, 56, who went on medical leave in January for an unspecified illness, was met with a standing ovation as he walked on stage at the Yerba Buena Theater to introduce the next-generation iPad.

"We think 2011 is clearly going to be the Year of iPad 2," he said.

The Internet had been buzzing for days ahead of Wednesday's event with speculation over whether Jobs, the technology visionary behind the iPhone, iPod, iPad and Macintosh computer, would make an appearance.

Apple shares surged after he turned up and were 0.85 percent higher at $352.29 dollars in afternoon trading on Wall Street.

The iPad 2 features front- and rear-facing video cameras to enable video chat and is thinner than the previous version.

"The new iPad 2 is actually thinner than your iPhone 4," said Jobs. "It is dramatically thinner, not a little thinner, a third thinner."

It weighs 1.3 pounds, down from 1.5 pounds, has the same 10-hour battery life as the previous model and will come in black and white versions.

"And we are going to be shipping white from Day One," Jobs said in a joking reference to Apple's continuing inability to produce a promised white version of the iPhone 4.

Jobs said the iPad 2 will sell for the same $499-$829 price as the previous model. It will ship in the United States on March 11 and on March 25 in 26 other countries including France, Germany and Japan.

Jobs said the iPad 2 is "dramatically faster" due to a new A5 chip. "The graphics in this thing are wonderful," he said.

Apple sold nearly 15 million iPads between April and December generating nearly 10 billion dollars in revenue.

"We've never had a product that got off to that fast a start," Jobs said. "We have 90 percent of the market.

"Our competitors were just flummoxed," he said. "They went back to their drawing boards, tore up their designs."

"I'm very impressed," Gartner analyst Van Baker said in a room where people were getting hands-on time with iPad 2 tablets. "The hardware is as good as anything else in the market but then the software just buries the competition."

By keeping the iPad 2 at the same price as its predecessor, Apple is "nailing it," according to the analyst.

The iPad 2 offers iMovie video editing software, music making suite GarageBand and "Hot Spot" software that lets tablets access the Internet by synching wirelessly to iPhone smartphones with telecom connections.

Rival manufacturers have been scrambling to bring their own tablet computers to market since Apple introduced the iPad last year.

Overall sales of tablets, which can be used to surf the Web, read electronic books, watch video and more, are forecast by Gartner to hit 55 million units this year.

The Consumer Electronics Show in Las Vegas earlier this year was rife with gadget manufacturers showing off tablets which they were racing to get into a market set ablaze by the iPad.

Motorola Mobility's Xoom, which went on sale last week, is the first tablet powered by Honeycomb software crafted specifically for such devices by Internet powerhouse Google, and has been heralded as a viable challenger to the iPad.

Another rival, South Korea's Samsung, has announced plans to come out with a large-screen version of its Samsung Galaxy Tab also powered by Honeycomb.

Jobs also announced Wednesday that Random House would be making 17,000 electronic books available for Apple's iBook store, joining other major publishers.

Jobs, who underwent an operation for pancreatic cancer in 2004 and received a liver transplant in early 2009, went on indefinite medical leave on January 17, turning over day-to-day operations to chief operating officer Tim Cook.