MOSCOW -- At least 14 people were killed and 28 injured Monday morning by a suspected suicide bomb attack on a crowded trolley bus in the Russian city of Volgograd -- the second such attack on mass transit in the city in as many days.
Ten passengers were killed immediately from the blast and four more died on the way to and in hospitals, officials said.
Russian law enforcement agencies said the explosion was a terrorist act and that they suspect a connection between Monday's attack and a suicide bombing on Sunday, less than 19 hours earlier, at the city's main railway station.
No group claimed responsibility for either of the attacks, the latest of several to hit southern Russia in recent months. Volgograd is close to the troubled Caucasus region, where Chechen rebel leader Doku Umarov has vowed to use "maximum force" to prevent Russia from staging the Winter Olympic Games, which he called "satanic games held on the bones of our ancestors."
Alexander Zhukov of the Russian Olympic Committee said in televised remarks that all necessary security measures have been taken to provide safety at the Olympic Games in February.
The death toll of the Sunday attack grew to 17, including the bomber, as a victim died overnight at a hospital, officials said.
"This is the second terrorist act in Volgograd over the two days, and investigators don't rule out that they could be connected," Vladimir Markin, spokesman for the Russian Investigative Committee, said in televised remarks. "Investigators are already questioning those passengers who survived the attack and whose condition allows them to talk with investigators."
"Now it can be preliminarily said that the explosive device was set off by a male suicide bomber, whose body's fragments were found and sent off for genetic testing to help identity him," Markin said. "The fact that the damage-causing elements in both explosive devices are identical proves the investigation's theory of interconnection between the two terrorist acts. It is possible that [both bombs] could have been prepared in the same place."
The Monday bombing took place near the Kachinsky market in downtown Volgograd and was powerful enough to shatter windows in nearby houses.
Rossiya-24, a Russian news television network carried dramatic images of the completely destroyed trolley bus, its charred ceiling crumpled and its sides blown off, with mangled debris strewn across the ground.
An Emergency Ministry plane delivered seven victims of the Sunday attack to Moscow for treatment, media reports said.