Hesham Genena suggested his assailants were linked to the government and said police denied him medical attention for hours after the attack outside his home.
Genena led Egypt's watchdog agency until President Abdel-Fattah el-Sissi fired him in 2016, following an investigation that concluded he had misled the public on the issue of corruption.
He spoke to The Associated Press late Wednesday.
Genena says: "I could have just been found dead in the desert like (Giulio) Regeni."
Regeni's brutal death triggered a crisis between Egypt and Italy.