Tragedy has struck London once again in the wake of an explosion at the Parsons Green Metro Station that left several people badly burned and hundreds of commuters running from the platform in panic. 

The Metropolitan Police said in a statement Friday that British authorities are treating the explosion at the subway station in southwest London as a "terrorist incident."

Officers have arrived at the scene and are investigating and will give more information as soon as possible, the statement added.

The blast left some passengers with facial burns and that paramedics were present at the scene, according to news agencies and witnesses.

Transport for London confirmed that Parsons Green station has been closed and there was no service between Earls Court and Wimbledon on the District Line which runs through Parsons Green. 

One witness reported seeing "a flash and a bang" in a bag holding the container, which is said to have had wires coming from it, on the packed rush-hour carriage.

"We were called at 8:20 a.m. to reports of an incident at Parsons Green underground station,” said Natasha Wills, assistant director of operations at London Ambulance Service.

"We have sent multiple resources to the scene including single responders in cars, ambulance crews, incident response officers and our hazardous area response team, with the first of our medics arriving in under five minutes.”

"There was panic as people rushed from the train, hearing what appeared to be an explosion," said BBC London presenter Riz Lateef, who was at Parsons Green on her way in to work. People were left with cuts and grazes from trying to flee the scene. There was lots of panic."

"Suddenly there was panic, lots of people shouting, screaming, lots of screaming,” said technology consultant Richard Aylmer-Hall, who was sitting on the "packed" District Line train.

"I saw crying women, there was lots of shouting and screaming, there was a bit of a crush on the stairs going down to the streets," he said.

The incident comes after a series of terror attacks that have rocked Britain this year, killing dozens of people and injuring hundreds, putting the capital on high alert.

British Foreign Secretary and former London mayor Boris Johnson appealed for calm. "I'm afraid my information is limited and it really is important not to speculate at the moment," he told Sky News.

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