A second blast in two days has struck the Russian city of Volgograd.
At least ten people have been killed in an explosion on a trolley bus.
Police and ambulances were quickly on the scene as emergency services treated the wounded.
Security had already been tightened up following Sunday’s suicide bomb attack on the city’s train station. The bombings come as the country prepares for the Winter Olympics.
Investigators have now confirmed at least 17 people died in the December 29 blast.
CCTV footage captured the moment of Sunday’s explosion.
Officials say the death toll could have been been worse, if it hadn’t been for 29-year-old police officer Dmitry Makovkin, who is said to have died preventing the suicide bomber from entering the main part of the station.
However there is confusion over just who was Sunday’s attacker – initial reports said it was a woman from Dagestan which is now the centre of a long running Islamist insurgency. But later the authorities said it could have been a man.
President Putin has put the country on high alert as Russia experiences its third deadly attack within four days. The Sochi Winter Olympics are about to start, however insurgents have vowed to use all means to prevent Putin from staging them.