He said the Tunisians, both students at a local college, and the Frenchman, who worked at a local hotel, were assaulted and beaten around 5:00 a.m. Moscow time (2:00 GMT) when returning from a night club.
All three sustained unspecified injuries, but were not taken to the hospital.
He said an investigation was under way.
People with non-Slavic features have repeatedly been attacked in apparently racially motivated crimes in Moscow, St. Petersburg and in many cases in Voronezh, home to many universities with foreign students.
A surge in violence targeting foreigners with non-Slavic features has prompted Russian and foreign human rights groups in recent months to raise concerns over the alarming spread of racist and xenophobic attitudes in the country.
