The incident which police have said is a “serious sexual offence” is reported to have taken place in the Priory Gardens park in Orpington yesterday evening (February 22).
Police say the victim, a teenage girl, was walking through the park on Saturday evening when the alleged offence took place.
A police cordon is in place and enquires remain ongoing.
A spokesperson for Metropolitan Police said: “Police are currently investigating a serious sexual offence allegation reported to have occurred against a teenage girl on the evening of Saturday 22nd February, when she was walking through Priory Park in Orpington.
“A cordon remains at the location to preserve the scene.
“Enquiries are ongoing.
“The victim is continuing to be supported by specialist officers.”