No arrests have been made and a crime scene is in place, the Metropolitan Police said.
Air ambulance and paramedic crews also attended - with the first medical responders arriving in six minutes, the London Ambulance Service (LAS) said.
It added: "We sent a number of resources to the scene, including ambulance crews, paramedics in fast response cars, an incident response officer and London's Air Ambulance.
"The first of our crews arrived in six minutes.
"Our crews treated three male patients at the scene, before taking them to London major trauma centres by road, as a priority."
The Met said it is waiting on an update on their conditions.
Anyone with information is asked to call 101 and quote CAD reference 3279/03Nov or contact Crimestoppers on 0800 555 111 to remain anonymous.