Yahoo Inc. (Nasdaq: YHOO) is buying Qwiki Inc., a mobile application that enables users to create videos on Apple Inc.’s iPhone. (Nasdaq: AAPL).

The move is yet another strategic step for Yahoo, which has become a serial acquirer in its quest to strengthen presence on smartphones, tablets and other mobile devices. This marks the twelfth deal for Yahoo since Marissa Mayer became CEO of the company in July 2012. She has led the once-struggling Sunnyvale, Calif. Internet company on a buying spree, with the $1.1 billion purchase of New York blogging service Tumblr Inc. the biggest recent deal. (For more, see “10 Startups Marissa Mayer Bought Before Tumblr.”)

In a blog post announcing the transaction, Yahoo did not disclose financial terms, but technology website AllThingsDigital pegs the price between $40 million and $50 million. The Qwiki application allows users to turn photos, music and videos into short movies.

“We will continue to support the Qwiki app, and the team will join Yahoo! in our New York city office to reimagine Yahoo!’s storytelling experience,” says the blog post.

Qwiki is led by CEO Doug Imbruce who co-founded the New York startup with Louis Monier, the founder of the AltaVista search site. Monier left the company in 2011. The company launched a publishing platform with Yahoo news partner ABC News in 2012 to create an application that combines photos, sound and video clips to create interactive stories quickly.

Qwiki has raised $10.5 million in venture capital to date. Among its most notable investors are Eduardo Saverin, co-founder of Facebook Inc. (Nasdaq: FB); Jawed Karim, co-founder of YouTube; and Pradeep Sindhu, co-founder of Juniper Networks. Venture capital firms Contour Ventures, Greylock Discovery Fund, Lerer Ventures and Tugboat Ventures also invested.