Terrified rush hour passengers were forced to evacuate Bank station in central London after a fight broke out.
Panicked commuters "ran for their lives" in a stampede as armed cops descended on the station shortly before 9am.
Many left their belongings abandoned in their desperation to get out, wrongly fearing there had been a terror attack.
One passenger likened the scene to a "horror film".
Shocked witnesses set off a fire alarm after a brawl broke out on a platform, forcing the busy transport hub - used by nearly 300,000 people a day - to shut.
A British Transport Police spokesman confirmed to Mirror Online that a fight had broken out inside the station.
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One horrified commuter wrote: "Had to run for my life a few minutes ago at Bank Station.
"Not even sure what happened in fact, but it’s the second time I’m caught in a stampede due to fear of a terrorist attack.
"People were being stepped on, leaving belongings behind. This is not normal."
She later described it as the "scariest moment of my life".
Another wrote: "People falling on the floor, luggage being abandoned, people screaming, staff members and passengers running for their lives. Was like something from a horror film."
Tom Lamb, 38, was travelling through the station when he saw two fellow passengers starting to throw punches at one another.
He told Mirror Online: "I got off at Bank and if you're walking from the Northern to Central, there's a left turn with some stairs and I saw these two guys having a fight as I was walking.
"Everyone started rushing out of the tunnel shouting 'run run' and then there was just a wave of total panic.
"Everyone started running in the other direction. I went just to look to see if it was a fight and there were two guys scrapping.
"It looked like one, who seemed to be a builder, punched the other, and then the second guy just went mental.
"It probably lasted three or four minutes, and initially there weren't guards around so people were trying to stop it.
"A lady came nearby and I told her not to go near it.
"It was such a feeling of panic - especially as these days I think everyone on the underground is on edge and ready to think the worst has happened."
Will Kinnon, who was at the station, wrote: "Was very scary being in a stampede running for what may have been our lives, not knowing what was happening."
Journalist Nick Pettigrew posted on Twitter : "Just been evacuated from Bank Station. A lot of people panicking, visibly upset. Almost a stampede in the escalators. No idea what the emergency is. Station staff dealing with it really well. Would avoid if possible."
Another commuter tweeted: "Something going on at Bank station - was crushed into lift with others with shouts of “run run”.. now emergency services arriving."
British Transport Police said: "We've been called to #Monument / #Bank station following report of a fight, during which the fire alarm was set off.
"There are no reports of weapons involved and no arrests at this stage, enquiries continue.
"Thanks for your patience whilst we responded, station reopening."
The Central Line's official Twitter account posted: "Bank / Monument station is closed while we respond to a fire alarm activation. District, Circle, Northern and Central line services are currently not stopping at this station."
The station reopened shortly before 9.30am.
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