US-based social games company Zynga is to acquire Canadian mobile app developer Five Mobile for an undisclosed sum, a move that is expected to help it expand beyond its Facebook focus. Reuters notes that, as part of the deal, four of Five Mobile’s employees will join Zynga and work at the newly created “Zynga Toronto,” the company’s first development studio in Canada.

Zynga is the top social games publisher on Facebook and its main revenue generator comes from selling virtual items such as tractors and weapons in games on personal computers. It is the company behind such popular games as FarmVille and Mafia Wars. It has taken steps to reduce its reliance on Facebook in recent months by acquiring companies focused on mobile games so it can come out with more games users can play on smartphones and tablets.

Last week Zynga filed with regulators for an IPO of up to US$1 billion. At the time of the filing, the firm noted: “We have limited experience developing games for mobile platforms. We expect to devote substantial resources to the development of our mobile games, and our limited experience makes it difficult to know whether we will succeed in developing such games that appeal to paying players or advertisers.”

The latest transaction is Zynga’s 15th acquisition in 13 months.