A woman and her daughter-in-law were on their morning walk at Bhandup on Tuesday.
Two men accosted them, whipped out a gun and told them to give them their jewellery.
An officer from Kanjurmarg police station, talking on condition of anonymity as he is not authorised to talk to the media, said: "Arpana Bhoir and her daughter-in-law Deepali, residing at RBI quarters in Bhandup were accosted by two men who came in a gold coloured van. They threatened the victims by brandishing a gun, asking them to part with all the jewellery they were wearing."
The women claim they were robbed of jewellery worth Rs 2 lakh. The accused then escaped in a car.
The officer added, "The victims had the presence of mind to note the number of the vehicle. After checking with the Regional Transport Office, we came to know that the registration number belonged to an autorickshaw. We suspect the accused were using a wrong number plate."
Senior police inspector R Wakale from Kanjurmarg police station said: "The incident took place at Kamal Sagar Road in Bhandup village which is normally a secluded spot. The victims, who reside in the vicinity, had gone for a morning walk around 6am. The incident took place around 6.15 am."
An officer added, "We suspect the accused must have kept a watch on the victims in the past couple of days. A case of robbery has been registered against the unidentified accused."