Video report by ITV News Security Editor Rohit Kachroo
A blast has ripped through an underground train in Russia's second-largest city, killing at least 14 people and injuring dozens more.
Here's everything we know so far:
At approximately 14:40 local time on Monday (11:20 GMT), an explosion ripped through an underground train in St Petersburg, Russia.
The explosion occurred as the train was travelling between Sennaya Ploshchad and Tekhnologichesky Institut stations.
Instead of stopping in between stations after the blast, the driver chose to continue to Tekhnologichesky Instituta.
Russia's Investigative Committee praised the diver for aiding evacuation efforts and reducing the danger of surviving passengers.
The entire St Petersburg underground system - which serves two million people a day - was shut down and evacuated.
Hours later, Russia's Anti-Terrorism Committee said they found and deactivated a bomb, rigged with shrapnel disguised as a fire extinguisher, at another station - Vosstaniya Square station.
Authorities in Russia identified a 23-year-old man from Central Asia for being responsible for the blast.
Intelligence officials in Kyrgyzstan have since identified the suspect as a Kyrgyz-born Russian citizen.
They said the suspect was a suicide bomber and carried an explosive device onto the train in a rucksack. He is believed to have links with radical Islamists.
Police believe the same man, not a second suspect, planted the bomb at Vosstaniya Square station.
President Putin says all causes are being considered, including terrorism - however Russia Prime Minister Dmitry Medvedev has described the blast as a "terrorist attack".