Consumers are activating more than half a million Android devices every day, an increase of about 25 percent from early May, according to Andy Rubin, who heads Google Inc's Android software business.

Google had said May 10 that 400,000 Android devices were being activated daily at that point. On December 8 Rubin had tweeted that daily Android phone activations had surpassed 300,000.

Rubin said the Android week-by-week growth rate is currently at 4.4 percent but he did not disclose, in his Tuesday announcement on Twitter, how many of the devices being activated are smart phones and how many are tablet computers, a relatively new competitive battleground in wireless devices.

Android smart phones have surpassed Apple Inc's iPhone in popularity as the Google software powers the main handsets of manufacturers such as Samsung Electronics Co Ltd, HTC Corp and Motorola Mobility Holdings Inc.

These companies have also developed tablet computers based on the Android software to compete with Apple's market-leading iPad. Google shares were up $11.58 or 2.4 percent at $494.38 on Nasdaq.

(Reporting by Sinead Carew; editing by Lisa Von Ahn and Gerald E. McCormick)