Thirty-five people were also reported to have been missing but officials have since confirmed that they have been found.
The blast happened at an ammunition depot near the city of Ulyanovsk, on the banks of the River Volga. The country's Federal Security Service said that the fires and blasts, which lasted for several hours, were caused as ammunition at the depot was being destroyed.
Governor Sergei Morozov said that ten people has been taken to hospital. He also reported that around 3,000 people from the surrounding area had been evacuated.
It was also reported that traffic in the area had gridlocked as people tried to flee the area. Houses in the area were reported to have had their windows blown out by the force of the blasts.
watching TV saw pictures of fire lighting up the sky above the city while it was described as being like a giant firework display by eyewitnesses.