The southern Russian city of Volgograd has been rocked by a second deadly explosion in less than a day.
The latest incident happened on a trolleybus during rush hour on Monday morning. Officials say at least 14 people were killed and more than 20 have been injured.
The trolleybus was destroyed during the morning rush hour. Photo: AFP
The bus bombing follows follows a suicide bombing at the city's central railway station, in which at least 17 people were killed on Sunday.
Monday's bomb went off just after 8am as the vehicle was pulling in at a busy stop where many people change onto trams in the Dzerzhinsky district, the BBC reports.
The first pictures from the scene show that the vehicle was almost completely destroyed and investigators immediately pointed to terrorism as the most likely cause.
Russian firefighters inspect the damage at Volograd train station. Photo: AFP
Investigators say they believe a male suicide bomber carried out the bus attack, while it is believed a female suicide bomber targeted the train station. No one has claimed responsibility for either explosion.
President Vladimir Putin has called for security to be stepped up at stations and airports throughout the country.
Moscow is concerned that militant groups could be ramping up violence in the run-up to the 2014 Winter Olympics in February.
The Games are to be held at Sochi, right on the edge of Russia's troubled Caucasus republics and their long-running Islamist insurgency, the BBC reports. Volgograd lies about 900km south of Moscow, 650km north of the North Caucasus and 700km north-east of Sochi.
Sunday's bomber detonated the explosives in front of a metal detector just inside the station's main entrance. Television footage showed a massive orange fireball filling the hall and smoke billowing out through shattered windows.
The head of Russia's Investigative Committee, Vladimir Markin, said the station was busier than usual with people heading home for new year holidays.
"The power of this explosion was the equivalent of 10 kilograms of TNT. There would have been many more victims if the guarding system at the train station hadn't worked. It didn't allow the suicide bomber to get through the metal detector into the waiting hall where at the time there were many people because three trains were late."
In October this year, a suspected female suicide bomber killed at least six people when she attacked a bus in Volgograd. On 27 December, a car bomb killed three people in the southern city of Pyatigorsk.
NZ athletes to compete
The New Zealand Olympic Committee said the attacks would not deter it from sending athletes to the Winter Games.
Chef de Mission Pete Wardell said there would be between 35 to 40 of its athletes, officials and coaches in Sochi. He said they have previously spoken to Russian authorities and are satisfied that the New Zealanders would be safe.
Mr Wardell said everyone was expecting there would be incidents in the lead-up to the Olympics, as the world's eyes are on Russia, but said it is the International Olympic Committee that would make a call if there was a major security issue.
