Second blast hits Russian city of Volgograd

  A blast struck the southern Russian city of Volgograd, killing at least 14 people  highlighting Russia’s security challenges as it readies to host the Winter Olympics in less than six weeks. Russian officials said a male suicide bomber is responsible for Monday’s explosion on a bus in the southern city of Volgograd that killed 14 people; the attack occurred just one day after a female suicide bomber killed 17 people at the city’s train station.

Authorities said about 20 people were wounded in Monday’s powerful blast, which occurred on a crowded trolleybus during the early morning rush hour. The attack destroyed the bus and blew out the windows of nearby buildings.

There was no immediate claim of responsibility for either explosion.

Earlier ten people were killed and another three were injured in an explosion at a railway station in southern Russia, on Sunday.

In October, a female suicide attacker blew herself up on a bus in Volgograd, killing seven people and injured dozens of others.