At least 10 people have been killed and 50 injured in a "terror attack" when a bomb exploded on a train in one of Russia's biggest cities.
Shocking images and videos are emerging from the station in St Peterburg, showing bloodied commuters and a subway carriage with its doors blown off almost reduced to rubble.
The explosions rocked a train travelling between 'Sennaya Ploschad' and 'Technologichesky Institute' stations at 2:30pm local time, according to Sputnik News.
Russian news agency Interfax said the device was an improvised bomb filled with shrapnel.
The Russian General Prosecutors Office has confirmed it believes the explosion was a terror attack.
Russian President Vladimir Putin was in St Petersburg today to meet his Belarusian counterpart, Alexander Lukashenko.
The entire St Petersburg metro system was evacuated and shut down by 15:40pm local time - just over an hour after the first explosion.
British Foreign Secretary Boris Johnson tweeted his sympathies to the victims and their families, saying he was "horrified" by news of the attack.
Russia has been rocked by attacks on its public transport system before.
In December 2013, two suicide bombings on a train and bus respectively killed 34 people in Volgograd. Just two months earlier, seven people were killed when an explosive belt was detonated on a bus in the same city.
In the Russian capital of Moscow, 40 people were killed and 100 injured in an attack targeting the metro system in March 2010.
The Moscow metro said it was taking unspecified additional security measures in case of an attack there, Reuters reported.