A bright flash was seen in the Chelyabinsk, Tyumen and Sverdlovsk regions, Russia's Republic of Bashkiria and in northern Kazakhstan.

Up to 150 people sought medical attention as a result of the incident, according to the Russian Interior Ministry. No serious injuries have been reported, with most of the injuries caused by broken glass and minor concussions.

Lifenews tabloid said that at least one piece of the fallen object caused damage on the ground in Chelyabinsk. According to preliminary reports, it crashed into a wall near a zinc factory, disrupting the city's Internet and mobile service.

The Emergency Ministry reported that 20,000 rescue workers are operating in the region. Three aircraft were deployed to survey the area and locate other possible impact locations.

Witnesses said the explosion was so loud that it seemed like an earthquake and thunder had struck at the same time, and that there were huge trails of smoke across the sky. Others reported seeing burning objects fall to earth.

The incident in Chelyabinsk bears a strong resemblance to the 1908 Tunguska event -- an exceptionally powerful explosion in Siberia believed to have been caused by a fragment of a comet or meteor.

According to estimates, the energy of the Tunguska blast may have been as high as 50 megatons of TNT, equal to a nuclear explosion. Some 80 million trees were leveled over a 2,000-square-kilometer area. The Tunguska blast remains one of the most mysterious events in history, prompting a wide array of hypotheses on its cause, including a black hole passing through Earth and the wreck of an alien spacecraft.