Close to 43 percent of mobile ads for the first quarter were delivered to Google Android devices compared to 38 percent sent to Apple iOS devices. Most mobile ads were sent to mobile phones, rather than tablets.

Mobile advertising company Opera Mediaworks reported, however, that iOS devices generated 52 percent of the total revenue compared for the period compared with 33 percent for Android. The report pointed out that Android's revenues for the first quarter of 2013 accounted for 27 percent of revenue. Most of Android's gain came at the expense of BlackBerry and Symbian devices.

Opera Mediaworks said Samsung Electronics was the clear leader in the Android market. The South Korean firm accounted for more that 60 percent of ad impressions on Android. Another South Korean company, LG, was a far second with its 11 percent.

Mobile phones received the majority of ad impressions for both Android and the iOS. Of Android's 43 percent market share, 41 percent came from ads on mobile phones while only 1.5 percent were on tablets.

Of the 38 percent of mobile ad traffic that was sent to iOS devices, 25 percent went to iPhones, 10 percent to iPad, and three percent to iPod Touch devices.

Social networks accounted for most mobile ad traffic volume but arts and entertainment sites were the top revenue generators. Business, finance and investing content had the highest revenue per impression. This segment has been at top for more than a year.

The US continues to drive the majority of ad traffic with over half the total market share but Asia has moved up, overtaking Europe as the second largest mobile ad market in the past quarter.