The Coptic Christian family of an Egyptian soldier said he was beaten to death by fellow officers because he was a Christian.
Joseph Reda Helmy, from the town of Kafr Darwish, had just completed training and was sent to his new unit in the afternoon. He was dead by evening.
Morning Star News reports army authorities called a cousin, Youssef Zarif, to claim the body.
The cousin demanded to talk to authorities, but one officer told him he had died from an epileptic seizure.
Suspicions were aroused because Helmy had been in excellent health before his death.
Zarif found bruises all over his cousin's body and severe injuries to his back. A doctor told Zarif that Helmy died of foul play rather than natural causes.
Zarif and another cousin said Helmy was targeted by officers for being a Christian.
One minister said women in Helmy's village are wearing black and photos of his body have been widely distributed.
An investigation led to the arrest of three officers. They are now in custody.
Helmy's case is not the first instance of minority Christians being targeted in the Egyptian army.
Morning Star News reported the deaths of two other Coptic soldiers who were killed. Authorities called them suicides, but in both cases the soldiers were in good mental health and one of them had severe bruising.