Update: police are treating the incident as a terrorist attack.
There are reports of an "explosion" at Parsons Green tube station in south-west London.
Metropolitan Police have issued a statement saying that they are "aware" of the incident.
Police and emergency services are currently at the scene.
https://twitter.com/metpoliceuk/status/908597086924525568
The London Ambulance Service has confirmed that people have been injured.
They are currently assessing "the level and nature" of the injuries.
https://twitter.com/Ldn_Ambulance/status/908603264949727232
Social media reports indicate that an "explosion" occurred on the train.
Passengers were then seen fleeing the station.
https://twitter.com/RRigs/status/908594792816349184
https://twitter.com/garthserg/status/908596986567421952
https://twitter.com/EmmaStevie1/status/908595323777486848
Police have confirmed that they are treating the incident as a terrorist attack.
https://twitter.com/metpoliceuk/status/908620962987433984
British Transport Police have said that Parsons Green station has been closed.
Commuters have been urged to use alternative routes.
More to follow.