Csatary had been in the hospital undergoing treatment for an unreported ailment and contracted pneumonia, daily tabloid Bors reported Monday.
The 98-year-old was arrested in July for his alleged role in sending 15,700 Jews to Nazi death camps, primarily Auschwitz, while he served as police chief in Nazi-occupied Kosice in spring 1944.
Kosice, now part of Slovakia, was known as Kassa, part of Hungary at the time.
Csatary allegedly regularly beat Jews irrespective of their gender or age with his bare fist and a whip for no particular reason, Hungarian news agency MTI reported.
He was convicted in 1948 in Czechoslovakia for his alleged crimes and sentenced in absentia to death, which was commuted to life in prison.
Csatary immigrated to Canada after World War II but was stripped of his citizenship in 1995. He then returned to his native Hungary.
Csatary was put under house arrest last year.
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