At least 10 people were killed and 10 others injured early Monday when an explosion hit a trolley bus in Russia's Volgograd, the second fatal blast within two days.  Photo taken on Dec. 30, 2013 shows the blast site of the trolleybus in Volgograd, Russia. Ten people were killed on Monday in a bombing that destroyed a packed trolleybus in the southern Russian city of Volgograd, the second attack in the city in two days after a suicide strike on its main train station, officials said. -- Photo: RIA NovostiRussian Investigation Committee spokesman Vladimir Markin said the fresh explosion could also be a terror attack, resembling the Sunday blast in the city's railway station that left at least 16 dead and more than 40 injured. A criminal case under the act of terrorism and illegal turnover of explosives has been opened.The Emergency Situations Ministry has sent a plane with medical modules onboard to attend the victims of the new explosion.Xinhuanet