Students hold placards during Nirbhaya Day to mark the anniversary of the brutal rape case of a 23-year-old physiotherapy student on a bus in New Delhi in 2012, in Ahmedabad on Dec 16, 2019. (SAM PANTHAKY / AFP)

NEW DELHI - The four men convicted of raping and killing a young student seven years ago will be hanged on March 20, ordered a court in Delhi on Thursday, after several rounds of mercy pleas from the convicts.

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The crime happened in December 2012 when a young medical student was brutally gang raped by six people inside a moving bus in south Delhi.

One of them committed suicide inside jail during trial, while another was acquitted on the ground of being a juvenile.

The remaining four -- Pawan Gupta, Vinay Sharma, Akshay Thakur and Mukesh Singh -- have been facing trial in the past seven years and their execution has been deferred three times. Each of them has filed mercy review petitions over the past few weeks.

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Asha Devi, the mother of victim Nirbhaya, said she hoped the execution would not be delayed again.