This is the latest wrap on this developing story from our news desk:
Several Russian media reports say there has been a deadly blast in the St. Petersburg subway system.
State-run news agency TASS cited an unidentified source as saying at least 10 people had died following an April 3 explosion.
Some reports said there were at least two blasts at separate locations.
The Lenta.ru news website cited an unidentified source as saying that at least five people were killed.
The state news agency RIA and other media outlets cited eyewitnesses as saying there were casualties.
There was no immediate statement from officials.
Footage and photos that were purportedly from the site and were posted on social media showed smoke in a metro station, and dead or injured people lying on a platform next to a damaged subway car.
A photo posted on the RIA website showed a subway car at a station with a door blown off and the interior mangled.
The authenticity of the images could not immediately be determined.
Based on reporting by RIA, Interfax, Life, Dozhd, and Meduza
Aftermath from blast in St. Petersburg metro.
There have been unconfirmed reports of a second explosion:
Video showing the aftermath of the blast.
Horrific photos from St. Petersburg:
Scenes after blast in St. Petersburg metro.
TASS are reporting that 10 people have died.
Putin says authorities probing all possible causes for the metro blasts in St. Petersburg, including terrorism.
Putin offers condolences to families of victims of St. Petersburg blast.