俄罗斯无轨电车再遭炸弹袭击
At least 12 people have been killed and more than 20 others hurt in a suspected suicide bombing on a trolleybus in the Russian city of Volgograd.
俄罗斯城市伏尔加格勒一列无轨电车遭疑似自杀式炸弹袭击，至少12人丧生，另有20多人受伤。
Witnesses described a scene of carnage following the blast
The blast comes a day after 17 people died in another suicide attack at the central station in the city.
Security has been tightened at railway stations and airports across Russia.
Moscow is concerned militant groups could be ramping up violence in the run-up to the 2014 winter Olympic Games in the city of Sochi.
The Olympic venue is close to Russia's volatile north Caucasus region.
Volgograd lies about 900km south of Moscow, 650km north of the North Caucasus and 700km north-east of Sochi.
Busy market
The latest explosion took place near a busy market in the city's Dzerzhinsky district.
Maksim Akhmetov, a Russian TV reporter who was at the scene of the blast, said the trolleybus was packed with people going to work in the morning rush hour.
He described the scene as "terrible", adding that the bus was "ravaged" and that there were "bodies everywhere, blood on the snow".
The explosion removed much of the bus's exterior and broke windows in nearby buildings.
The figures given for the number of dead and injured are still fluctuating - and a one-year-old child is said to be among the victims.