The three officers are accused of detaining the man on suspicion of theft on the night of October 28-29, and then beating a confession out of him.
When he then refused to sign his "admission of guilt," local media say he was "taken to the edge of the city and burned alive."
The dead man has been officially identified as 30-year-old Armenian national A. Gasparyan.
Saratov Region police have been criticized in the Russian media for only making the news public on the evening of October 30, after local journalists had already written about the incident.
This is not the first case of its kind in Russia this fall. In September, in Russia's Far Eastern Primorye Territory, three police officers were arrested on charges on beating a man to death near the city of Vladivostok. The same charges were also brought against two other officers in the city later that month.