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 bus bombing follows follows a suicide bombing at the city’s central railway station, in which at least 17 people were killed on Sunday.
Moscow is concerned that militant groups could be ramping up violence in the run-up to the 2014 Winter Olympics in February.