Four thousand tonnes of old munitions blew up at a military site in central Russia on Tuesday, releasing a plume of white smoke into the sky and sending panicked locals fleeing for their lives.

The Donguz military range 30 kilometres (18 miles) south of the city of Orenburg in the Ural mountains region caught fire after the old munitions unexpectedly exploded, the emergency and defence ministries said.

A total of 4,000 tonnes of outdated munitions including 400 tonnes of aerial bombs and more than 1,300 tonnes of shells exploded, a spokeswoman for the chief military investigative directorate, Yevgeniya Maltseva, told AFP.

The defence ministry and the regional government said no military personnel or local residents had been injured.

Television footage showed a white mushroom cloud rising above the area.

"It was mostly residential areas close to the military range that sustained damage," the regional legislature said in a statement, adding that the force of the blasts also shattered windows of schools and kindergartens.

Witnesses from nearby villages described scenes of chaos.

"First there was a first explosion. We got scared. We ran out of the house at once. Then a second explosion followed, then a third one. It was terrible," one resident Yelena Churikova said in televised remarks.

"Glass flew around. Everything started falling from the upper floors. A neighbouring house cracked in half. You can't imagine that sight. Everyone ran outside, everyone is yelling. No-one understands what is going on."

The Russian military has a huge stockpile of outdated munitions that are poorly maintained and frequently explode, causing casualties and deaths.

Last July, more than 20,000 people had to be evacuated and dozens were injured when a fire at a munitions depot in the Volga region of Udmurtia triggered a succession of explosions and sent a fireball blazing into the sky.

The regional government said officials were assessing the damage from the blasts in three villages close to the military range as well as in Orenburg.

A spokesman for the regional emergencies ministry, Vladislav Zubchenko, did not say how many people were evacuated from the affected area, which is home to several thousand people.

Officials were conducting aerial reconnaissance and several ambulances and psychologists had been dispatched to the area.

A defence ministry commission flew down to the military range to look into the accident, ministry spokesman Igor Konashenkov said in televised remarks.

The governor of the Orenburg region, Yury Berg, was forced to leave early from a meeting in the Kremlin chaired by President Vladimir Putin following reports of the blasts.

"Yury Alexandrovich, do you have to leave?" the state RIA Novosti news agency quoted Putin as asking Berg at the meeting.

"Yes, thank you," the governor responded before making his exit.

The regional legislature was planning to appeal to construction companies for help with clearing up the aftermath of the accident.