U.S. Internet users watched more than 10 billion videos in December, as the Hollywood writers strike kept new TV shows off the airwaves and drove consumers to the Web, a market researcher said Friday.

Nearly 141 million Americans watched online video during the last month of 2007, with Google's sites capturing the largest audience with 79 million viewers, ComScore said. Google's YouTube accounted for more than 97% of all videos viewed on the search engine's sites.

Google's market share in terms of viewers was 43%, followed by Fox Interactive Media and Yahoo sites, which had 23.9% and 20.8% of the market, respectively. In terms of the number of videos watched, Google held 32.6% of the market, followed by Fox at 3.5% and Yahoo at 3.4%.

December represented a "considerably strong month" for online video viewing, which was boosted by the ongoing Hollywood writers strike. "With the writers strike keeping new TV episodes from reaching the airwaves, viewers have been seeking alternatives for fresh content," Erin Hunter, ComScore's executive VP of media and entertainment, said in a statement. "It appears that online video is stepping in to help fill that void."

On YouTube, 77.6 million viewers in December watched an average of 41.6 videos apiece. On Fox's MySpace, the Web's most trafficked social network, 40.5 million people watched 334 million videos.

Video lovers watched an average of 3.4 hours of video during the month, representing a 34% gain since the beginning of 2007. The average online video lasted 2.8 minutes, and the average viewer watched 72 videos.