Police were called to reports men were seen with a gun inside a car at around 4.50pm.
The car failed to stop for the police and then smashed into another vehicle. The occupants of the car then abandoned it and attempted to flee the scene.
Police cordoned off a section of Burdett Road and had a helicopter hovering over the area during the incident, according to witnesses.
Shocked bystanders said police chased one man into Mile End Park Leisure Centre off Burdett Road.
Trainee solicitor Can Ozkutan, 27, from Mile End, was on his way to the gym when the dramatic incident unfolded.
He told the Standard: “I was talking to a friend outside the gym when I heard lots of shouting round the corner.
“We looked round and the police officer had one guy down on the floor and was pointing a gun at his head and shouting at him not to move.
“Then there was a another guy who ran off around the stadium and another that ran into the gym, straight past us.”
“Police ran into the gym after the guy and that is when they got a sniffer dog and a police helicopter to try and find him.”
Mr Ozkutan said he was kept in the gym for half-an-hour while armed police hunted the suspect.
Photographs taken by Mr Ozkutan show a man on the floor with his arms outstretched with an armed officer over him.
A police spokesman said: “Police were called regarding males in a car seen with a firearm.
“This car failed to stop for police. In Burdett Road, this car was in collision with another vehicle.
“The occupants abandoned the car and attempted to flee the scene. Armed officers detained three suspected occupants from the car.