The global mobile-game market is expected to increase nearly fivefold from $3.77 billion in 2010 to $17.6 billion in 2015, according to the research arm of Tokyo-based Ichiyoshi Securities. The war is taking place on smartphones with names like Gree, DeNA, Zynga, Apple and Google.
Zynga has a massive base of people familiar with its games, like "Farmville" and "Words with Friends," on Facebook. But it is still relatively new to mobile games.
The rivalry is heating up at a time when the fragmented mobile-game world is starting to consolidate. Gree bought game maker Funzio for $210 million last month, giving it popular titles such as "Modern War" and "Crime City." Zynga purchased OMGPOP, the maker of hit game "Draw Something," for $183 million in March.
Zynga lags the Japanese companies in converting game players into paying customers.