Mitsui Sumitomo Insurance Group Holdings, Inc., Aioi Insurance Co. and Nissay Dowa General Insurance Co. announced Friday they have agreed to merge in April 2010, in a move that will create Japan's largest nonlife insurance group.

The integration plan comes as slumping car sales hit automobile policy sales — a key nonlife insurance business.

Analysts also predict the latest move may trigger further mergers in the industry as firms battle to survive the harsh business environment.