Prakash was rushed to the Thapathali-based Norvic Hospital early this morning, where he was pronounced dead.
Addressing a press conference, Dr JP Jaiswal of Norvic Hospital said Prakash was dead around three hours before he was admitted to the hospital at 5:50 am this morning.
"His eyes were unresponsive and there was no pulse when he was brought to the hospital," said Jaiswal.
"In 90 per cent of such cases, patient suffers a severe cardiac arrest," he added.
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Prachanda arrived at the hospital in Kathmandu from Jhapa, where he was attending election campaign for the upcoming elections.
President Vidya Devi Bhandari reached Prachanda's house in Baluwatar to express condolences on the demise of his son.
Prime Minister Sher Bahadur Deuba, CPN-UML chairman K P Oli and other senior leaders have also expressed condolences.
The news of Prakash's death comes two weeks before the first phase of provincial and parliamentary elections.
Prakash's wife Bina Dahal is contesting election for the Parliament from Kanchanpur district.
Prachanda had one son and three daughters. One of his daughters died four years ago. She was suffering from breast cancer.