The news agency PAP cites Jaruzelski's daughter, Monika Jaruzelska, as saying that the 89-year-old former leader was taken Wednesday to a Warsaw hospital after several spells of bleeding in recent days.
Jaruzelski's wife, Barbara Jaruzelska, was earlier quoted by the TVN24 broadcaster as saying his condition is "very serious." But his daughter said his life is not in danger.
Jaruzelski has suffered from serious health problems in recent years, including cancer for which he underwent chemotherapy.
Jaruzelski's hospitalization comes on the eve of the 31st anniversary of martial law, a repressive crackdown that he ordered against Lech Walesa's Solidarity movement in an attempt to crush the proponents of democracy.