Officers were called to Gravelly Hill when the animal attacked members of the public at around 2.45pm on Thursday.
The victim was pronounced dead at the scene. Formal identification is yet to take place but her next of kin have been informed, the force said.
A second woman was taken to hospital with dog bites but her condition is not life-threatening.
Armed officers attended with support from the National Police Air Service and seized seven dogs in total.
Chief Inspector Alan Sproston said: “Our thoughts are with the family of the woman who sadly died this afternoon. This incident will be concerning to the local community and I would like to reassure them that we believe all dogs have been accounted for and are in police custody.
“Our investigation to establish the circumstances of the incident remains ongoing and we would ask the community not to speculate.”
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