More than 177 million U.S. Internet users watched video content in June, according to the latest report from comScore.

Google sites, driven by video viewing on YouTube, ranked as the top video content property with 144.5 million unique viewers, followed by Yahoo sites (44.9 million viewers) and Vevo (43.7 million viewers).

Google sites had the highest number of overall viewing sessions with 1.8 billion and average time spent per viewer at 261 minutes or 4.3 hours. Hulu also had high viewer engagement with an average of 135 minutes (or 2.2 hours) per viewer.

Americans viewed more than 4.3 billion video ads in June, with Hulu generating the highest number of ad views at 566 million. Tremor Media Video Network ranked second overall (and highest among video ad networks) with 524 million ad views, followed by BrightRoll Video Network (333 million) and Microsoft Sites (222 million).

Video ads reached 45 percent of the total U.S. population an average of 31.5 times during the month. Hulu delivered the highest frequency of video ads to its viewers with an average of 24.2 over the course of the month.

Other highlights include:

*84.6 percent of the total U.S. Internet audience viewed online video.                                             

*The duration of the average online content video was 4.9 minutes, while the average online video ad was 0.4 minutes.

*Video ads accounted for 12.2 percent of all videos viewed but only 1.2 percent of all minutes spent viewing video online.

comScore

also introduced its new Video Metrix 2.0 online video measurement service offering improved reporting of online video ad impressions.