Six major nonlife insurers on Wednesday posted pretax losses for the business year to March as the global economic downturn caused securities revaluation losses.

Sompo Japan Insurance Inc., the nation's second-largest nonlife insurer, incurred the largest group pretax loss — ¥144.05 billion — after losing ¥147.9 billion on financial guarantee insurance and losses on securities holdings. It booked a ¥94.06 billion profit the previous year.

Aioi Insurance Co. followed with a ¥23 billion pretax loss.