( Reuters ) - At least eight people were killed and 43 were injured on Wednesday in an explosion on a bus in the Russian city of Togliatti and authorities said they were treating the suspected bombing as a terrorist act.
The early morning explosion on the bus, which came as people travelled to work in the rush hour, was probably caused by up to 2 kg ( 4.4 lbs) of explosives, local police sources were quoted by local news agencies as saying, larger than initially stated.
"We have reached the conclusion that this was an act of terrorism," the Samara region governor Vladimir Artyakov said in comments broadcast by Russia's Vesti-24 news channel.
"We are clarifying what type of explosive device was used and we are also clarifying the possibility that there could be more victims."
The officials gave no indication of who might be behind the blast. The Russian prosecutors tend to use the term "terrorism" broadly to describe almost any deliberate attack which incurred big casualties.
In one picture taken by an emergency worker at the scene, the body of one woman could be seen still sitting upright inside the bus.
Other pictures showed the bloody remains of victims, with clothes ripped from bodies -- face down in the debris -- and limbs hanging through blown out windows of the devastated bus.
"Eight people are dead, fifty are injured, with ten rescue groups involved. The first arrived within five minutes of the explosion and more soon after," said Vladimir Markhin, the Togliatti representative of the Russian investigation committee.
Prosecutors had also opened criminal cases for murder and the illegal storage of explosives, Russian media reported.
"There is reason to believe that the explosive was planted either underneath or on the floor of the bus," the police source was quoted as saying.
Togliatti, an industrial city on the banks of the Volga river, is more than 1,000 km ( 620 miles) southwest of Moscow and home to the country's biggest carmaker, AvtoVaz, and is sometimes called Russia's Detroit.
Russia's President Vladimir Putin phoned his envoy to the Volga region and ordered that "every possible measure to give medical assistance to those injured and to help the families of those killed," should be provided, Interfax said.
Organised crime groups, many of them involved in the trade in car parts, fight regular turf wars and gangland killings are common. But Togliatti is far from the troubled North Caucasus region.
Explosive devices without shrapnel, like the one Russian media said may have caused the bus explosion, are frequently used to settle scores in business feuds.