Witnesses to the London underground explosion have reported seeing a 'stampede' of people fleeing from the area, some with serious burns to their face and body.
A fireball is reported to have erupted on a train at the Parsons Green underground station at approximately 8.20am local time.
The Met have released the following statement regarding the incident.
"Officers from the Met's Counter Terrorism Command are investigating an incident on a London tube train this morning.
"Police were called at approximately 8.20am BST on Friday, 15 September to Parsons Green Underground Station following reports of a fire on the train.
"Deputy Assistant Commissioner Neil Basu, the senior national coordinator for CT policing, has declared this a terrorist incident.
"Officers from the Metropolitan Police Service and British Transport Police attended the scene, along with colleagues from the London Fire Brigade and London Ambulance Service.
"At present we are aware of a number of people who have suffered injuries.
"It is too early to confirm the cause of the fire, which will be the subject to the investigation that is now underway by the Met's Counter Terrorism Command. The station remains cordoned off and we are advising people to avoid the area."
Witnesses have described the chaos which ensued after the explosion, with reports that commuters sustained crush injuries in the hurry to escape.
"I heard and bang and there were people charging at us outside," one witness told the UK Daily Mail.
According to this witness, the injured people were taken to a nearby cafe as a refuge point so they could be treated for their injuries.
One person posted on Twitter that they had to run onto the tracks at the station to safety.
It is believed that there are 20 people who sustained injuries in the explosion.
The blast appears to have come from a white plastic bucket inside a Lidl supermarket bag.
Train services in the area have been halted, with a large presence from emergency services at the scene.
Reports have been circulating on social media that there was a man armed with a knife and a second explosive device, but these are unfounded claims and appear to be mere speculation.
Prime Minister Theresa May will chair a meeting of the government's Cobra emergencies committed to discuss the incident.