Police were called at approximately 19:46hrs on Tuesday, 26 June to reports of a robbery in Mayesbrook Park, Barking.
It is believed that the victims, two males aged in their late teens, had been approached by a group of five men who attempted to take their pedal cycles.
When the victims attempted to prevent their bikes being stolen, one of the group revealed a machete.
The victims then handed over their red bikes.
It is also believed the rest of the group were carrying knives.
At this stage there have been no arrests, and enquiries continue.
Officers from The Met’s East Area Command Robbery Unit are investigating.
Anyone with information is asked to call 101 or Crimestoppers on 0800 555 111.