Londoners using the city's tube system were forced frantically smash windows after smoke began filling one of the trains.

The emergency sparked chaos as passengers tried to escape the dangerous situation through train windows.

The shocking scenes were captured from Clapham Common by a fellow commuter who filmed every minute of the ordeal.

In the video that was posted to Twitter, passengers can be heard crying out for help while others tried to escape.

The distressing footage also showed Londoners trying to pry the doors open with them seemingly being stuck.

Once one of the windows was smashed, dozens of passengers can be seen clambering out from the carriage.

'Carriages were filling with smoke' as Londoners attempted to escape tube fire

One London tube user told the Mirror how the train began filling up with smoke as people attempted to escape.

They said the doors wouldn't open with workmen having to save the day as they smashed the windows with their tools.

The trapped person said: "There was a smell of smoke on the train, the train went down about 5 carriages into the tunnel and stopped, the train on the opposite side pulled in and people were running to get off the platform, the whole time the carriages were filling with smoke and the doors did not or would not open and when we tried to open them they only opened maybe 10cm thanks to the workman on the platform on their way home they had hammers and other tools to smash all the windows for everyone to get out, no response from station staff at all even with everyone’s scream for help."