TOKYO -- Hyosuke Niwa, 79, a former Japanese labor minister, died Nov. 2 at the Aichi Medical University Hospital in central Japan.

Mr. Niwa had been in a coma since being stabbed 12 days ago by a mental patient, officials said. His death was attributed to a heart attack caused by excessive bleeding.

An autopsy report revealed he was given the wrong type blood during emergency transfusions, which could have contributed to his death, officials said. Mr. Niwa, who had type O blood, was given type B blood during transfusions at two hospitals, according to the autopsy by medical staff at Nagoya University.

Officials suspect the transfusion mistake may have hastened Mr. Niwa's death, Kyodo News Service reported. Mixing blood types can cause red blood cells to rupture and clump together.

Mr. Niwa was attacked Oct. 21 while walking to a military ceremony at the Moriyama military base in Nagoya, 170 miles west of Tokyo. He was stabbed by a 47-year-old mental patient with a knife, police said.

A 12-term member of the governing Liberal Democratic Party in the Diet, Mr. Niwa was labor minister from December 1988 to June 1989 in the cabinet of Prime Minister Noboru Takeshita.

Survivors include his wife, a son and three daughters.