Munich Re is facing the possibility of its financial strength rating being downgraded by ratings agency Moody's.
Its current AA1 security has been called into question as a result of falling values of its shareholdings and worries over its earnings.
Moody's expressed concern about Munich Re's capitalisation because of the reduced value of its cross shareholdings, including its holding in insurer Allianz.
The agency said it expects Munich Re's earnings to be hit by falling investment returns and possible high charges for claims.
Moody's said it would review the subjects and assess the group's relative risk-based capital strength.