Two towns were evacuated in Russia after a military ammunition dump exploded in the southern Orenburg Oblast region.

Authorities said more than 4,000 tons of ammunition blew up a few miles away from the rail station of Donguz, about 1,000 km south of Moscow.

"That included 1,379 tons of 100-mm shells, 400 tons of aviation bombs, and 2,000 280-mm rockets from Uragan multiple rocket launchers," military officials said.

Three massive blasts were heard around 1 pm by the local population. Windows were shattered and trees tore down in Donguz and in a nearby unamed town, local press reported.

Authorities evacuated 10,000 inhabitants from the two towns for security reasons.

Shockwaves were also felt in Orenburg, the region capital, 40 km form the scene of the incident.

A video showing a huge smoke cloud rising from the Russian steppe was posted on YouTube.

Military officials said no one was killed in the blasts.

According to early reports, a fire broke out for yet unknown reasons, as soldiers were unloading ammunitions from a train.

Officials said that the alarm was launched as some militaries spotted a suspect smoke and that the 300 militaries working in the area had just enough time to run away and find shelter before the ammunitions to explode.

"Commander issued an order to leave the premises. We dropped everything and fled. Otherwise all the 300 people would have been killed," an eyewitness told Russian newspaper Izvestia.

"The situation is being monitored by reconnaissance and mine-sweeping groups," a military spokesman said.

In a similar incident a Russian military train carrying ammunition caught fire and blew up in Siberia earlier this summer.