"It's a heinous crime. It is very upsetting," he said about Sunday night's incident while receiving a delegation of women MPs on the issue.
Agonised at the incident, Dr Singh told the delegation that he had directed the home minister to take all measures to ensure that culprits are brought to justice and such cases do not recur, sources said.
The remarks came as Parliament continued to witness anger with members seeking adequate protection for women in the backdrop of the barbaric incident of rape of a 23-year-old girl.
Congress spokesperson Renuka Chowdhary said the PM assured a delegation of women MPs that he will discuss the issue with his Cabinet colleagues to tighten the system. "The PM was extremely distressed after hearing the incident," she added.
The delegation was led senior Congress MP from Rajya Sabha Mohsina Kidwai.
A delegation of women MPs will also be meeting Delhi Lieutenant Governor Tejinder Khanna to seek better security measures, Chowdhary said.
"This incident cannot be allowed to remain mere statistics. We will keep the issue alive so that there is no recurrence of such incidents," she said.