Russia was the world’s sixth most dynamic market for mobile ad requests and impressions on the Opera Mediaworks platform in the second quarter of this year, according to the Q2 2013 State of Mobile Advertising report, which was released last week by the Norwegian company.

In Q2 2013, the Russian market joined the group of the most advanced countries in ad requests and impressions which, includes the UK, Indonesia, Italy, and India.

The United States drives the majority of ad requests and revenue on the Opera Mediaworks platform, but it is seeing a slight drop in global market share. In Q1 2013, the U.S. share of requests was 50.67%, while this quarter it represents 49.3% of the market.

On this key market, Opera Mediaworks found that mobile sites and apps in the Music, Video & Media category had received the most ad impressions in the second quarter, while the Sports category raced to the top in revenue generation, driven by the opening of the U.S.’ baseball season.

The research also revealed that during the reporting period advertisers running rich media in-app campaigns had outsmarted those serving ads through standard banners and the mobile web.

According to the report, iOS is the “clear market leader” among operating systems worldwide in both impression volume and revenue generation, “capturing nearly 44% of all ad impressions and almost half of all revenue.”

In Russia, however, this operating system holds a very limited market share, according to the latest market data.