The incident, which was caught on CCTV, occurred around 7.30 AM when 60-year-old Vinod was alone in her house in Gandhi Vihar area, a senior police officer said.
The woman told police that she had responded to a doorbell and as soon as she opened the door the duo barged inside, he said.
After threatening her at gun point the duo tied her down and thrashed her to know where she had kept money and jewellery, the officer added.
It is suspected that they at some point of time were tenants of the woman, the officer said.
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A case was registered under relevant sections of IPC at Timarpur police station.
The woman has a married daughter who lives in Ludhiana while she lives alone at Gandhi Vihar.
Investigators are also checking the call details of the woman to find out if someone known to her was involved in the robbery.