SAN FRANCISCO -- Google (GOOG) introduced its new flagship Nexus 5 smartphone Thursday, along with a new version of the Android software that's aimed both at high-end consumers and a vast audience of potential Android users in developing countries.

The new phone, designed to show off the latest version of Android known as KitKat, is sleek, light and boasts a souped-up camera and other new features. But KitKat itself has been engineered to require less memory, so it will work just as well on lower-cost smartphones sold in countries like Brazil, India and Russia, according to Google executive Sundar Pichai.

Most Android phones sold in those countries now are so limited in memory that they have to run a much older version of the software known as Gingerbread, which was first introduced in 2010 and won't support a host of newer applications and services that Western consumers use routinely, he said.

While more than 1 billion Android gadgets have been activated around the world, KitKat is part of Google's strategy to reach "the next billion," said Pichai, who is Google's senior vice president for Android and Chrome software. Google lets other phone-makers use Android without charge, because Google makes money by showing ads to consumers who use Google's online services.

The new Nexus 5 phone, manufactured by LG in partnership with Google, goes on sale Thursday in the Google Play online store and will be available in retail outlets in coming weeks, Pichai said. It's priced at $349 for a version with 16 gigabytes of memory and $399 for a 32-gigabyte version; both are unlocked, which means they come without a contract from a cellphone service provider.

Google has released a series of Nexus phones over the past five years as a way to show off its software and encourage other companies that use Android to incorporate the latest features. Manufacturers can decide independently when they want to offer the latest Android version, and cellphone service providers set their own schedule for updating older devices their customers are already using.

That's led to what some analysts say is a major weakness in the Android ecosystem: It's harder for developers to create new Android apps, since the market is "fragmented" among different versions of Android on different gadgets, said Avi Greengart, research director at Current Analysis. By contrast, the majority of Apple (AAPL) iPhone users are all using the latest version of Apple's mobile software.

Google's efforts to make KitKat work on lower-end phones in emerging markets could help counter that fragmentation, Greengart said.

The new Nexus 5 phone has a 5-inch screen designed to show photos and other images across the full screen, rather than cutting them off to make room for a toolbar and other icons. Its camera has a gyroscope designed to smooth out vibration and new software that adjusts for poor lighting conditions or moving subjects.

Other new features in the KitKat software include closer integration with Google's search function, with more sophisticated voice-recognition and location-based services -- such as the ability to use the phone's calling app to search for businesses that are geographically close to wherever the phone user happens to be.

Pichai also demonstrated a pilot program that's expanding the Google search function to include mobile apps as well as the wider Web. The program will allow a smartphone user, for example, to search for a restaurant and get results that include websites and a page within the OpenTable reservation app, with information about the restaurant.

Contact Brandon Bailey at 408-920-5022; follow him at Twitter.com/BrandonBailey.