Fourteen people are reportedly dead and 28 were wounded after a bomb exploded on a trolley in the Russian city of Volgograd on Monday, Reuters reported.
The attack, carried out by a suicide bomber, occurred just one day after a suicide bombing in Volgograd killed 17 people. The attacks increased fears of more deadly attacks on the Sochi Winter Olympics to be held in Russia in February 2014.
"For the second day, we are dying," one woman near the site told Reuters while holding back tears. "It's a nightmare. What are we supposed to do, just walk now?"
The trolley was crammed with people traveling to work when it exploded at around 8:30 a.m. local time, (11:30 p.m. in New York). The bus was completely destroyed.
"The explosives were detonated by a male suicide bomber, fragments of whose body have been found and taken for genetic analysis to establish his identity," Vladimir Markin, spokesman for Russia's Investigative Committee, told Al Jazeera.
A female suicide bomber is suspected to be behind the Sunday attacks that killed 17 people at a Volgograd railway station. Markin told Al Jazeera the two bombings are most likely related. The bomber in Monday's attacks detonated four kilograms of explosives, which were similar to the ones used in the railway attack.
"This confirms the theory that the two attacks are linked. It is possible that they were prepared in the same place," Markin told Al Jazeera.
No group has yet claimed responsibility for the attacks, Reuters reported.
Volgograd, with a population of nearly one million, is a central transportation city that lies close to unstable territories in North Caucasus, NBC News reported. A woman from North Caucasus, an area known to house Islamist militants, carried out a suicide bombing on a Volgograd bus in October that killed several people.
President Vladimir Putin ordered increased nationwide security after Monday's attacks. Putin previously dismissed threats from militants in the North Caucasus area, hoping that the Winter Olympics will boost his image, Reuters reported.