Apple Inc. announced on Wednesday that it would hold its annual Worldwide Developers Conference (WWDC) in San Francisco from June 11-15.

The conference will focus on Apple's mobile operating system iOS and desktop operating system OS X Mountain Lion, featuring more than 100 technical sessions presented by Apple engineers as well as the Apple Design Awards, a showcase of the most outstanding apps from the past year, said the company based in Cupertino, California.

During the conference, key executives of the company will also deliver speeches about the future for the operating systems.

"We have a great WWDC planned this year and can't wait to share the latest news about iOS and OS X Mountain Lion with developers," Philip Schiller, Apple's senior vice president of worldwide marketing, said in a statement.

According to Apple's website, tickets for the conference, with a price tag of 1,600 U.S. dollars per person, were sold out in less than two hours.

The key announcement at this year's WWDC is likely to be iOS 6, the sixth generation of Apple's mobile operating system, rather than a new generation of iPhone.

At the WWDC of past years, Apple announced the iPhone 3G in 2008, the iPhone 3GS in 2009 and the iPhone 4 in 2010, but it broke the pattern last year by introducing the iPhone 4S at a separate event in October.

After Apple's WWDC, Google will hold its annual developer conference Google I/O from June 27-29. With a similar lineup as Apple's conference, Google is expected to introduce the latest generation of its Android mobile operating system, which is reported to be codenamed Jelly Bean.

Google is also rumored to release a Nexus-branded tablet powered by Android. The device is seen as Google's competitive tablet product that could have a strong second place in the market following Apple's iPad.

As the current mobile market is dominated by iOS and Android devices, Apple WWDC and Google I/O will make June a key month for smartphone and tablet app developers.

Meanwhile, Research In Motion will hold its Blackberry World 2012 event from May 1-3, and the landing date of Microsoft's Window Phone "Tango", an update to the software giant's mobile operating system, is also reported to be in June.