The head of games for Rovio the company behind the hit game Angry Birds has resigned and the company has closed its London studio.

Wilhelm Taht resigned on the weekend leaving CEO Kati Levoranta in charge of games. The Finnish company has warned that its brand licensing revenues could decline 40 percent this year.

Rovio has blamed tough competition and higher marketing costs for the poor outlook. It issued a profit warning last month and its shares have se fallen 50 percent.

The company said it is closing its London studio because it wants to concentrate on its remaining studios in Finland and Sweden.