After the incident, in which three people were injured, the “Section 60” regime was introduced in the center of the British capital.
The victims are in a stable medical condition, Met Police said.
Emergency services rushed to the scene at 7.28pm following reports of a disturbance near the Serpentine pond.
The four men arrested are being held in police custody, and officers have appealed for witnesses or anyone with video footage to call them on 101 quoting CAD 8150.
A Section 60 order, which gives police the power to stop and search anyone in the area, is in place for the borough of Westminster until 6am on Sunday.
