The incident happened in Rectory Lane near to Foots Cray Meadows at 10.43am today (October 10).
At the scene, a woman in her 20s was treated for serious injuries.
She was taken to hospital, and her injuries are not believed to be life-changing or life-threatening.
Another woman was also taken to hospital with injuries to her arm.
Police have arrested three women on suspicion of grievous bodily harm with intent.
They currently remain custody.
Just before 1pm today, multiple forensic officers were spotted investigating the matter.
A Metropolitan Police spokesperson said: “Police were called at 10:43hrs on Friday, 10 October to Rectory Lane, Sidcup following reports of an assault.
“Officers attended with the London Ambulance Service and a woman in her 20s was treated for serious injuries. She was taken to hospital and her injuries are not believed to be life-changing or life-threatening.
“Another woman was also taken to hospital with injuries to her arm.
“Three women have been arrested on suspicion of grievous bodily harm with intent. They remain in custody.”
