The four men convicted in the gang-rape and murder of a 23-year-old physiotherapy student in Delhi in December 2012 were executed by hanging at Tihar Jail at 5.30am on Friday.

The victim was attacked by the group when she and a friend boarded a bus the assailants were driving. She was abandoned by the gang with gruesome injuries and succumbed in hospital two weeks later.

The crime, which became known as the Nirbhaya case in memory of the honorific given to the victim, shocked the country, triggering mass protests and leading to demands for changes in prosecution of rape cases.

The four convicts—Mukesh Singh (33), Pawan Gupta (26), Vinay Sharma (27) and Akshay Kumar Singh (35)—had been convicted of gang-rape and murder in September 2013 and sentenced to death. Another accused, who was a minor at the time of the crime, was placed in a juvenile home and released in late 2015.

The fifth suspect, Ram Singh, who was Mukesh Singh's brother and believed to be the mastermind of the crime, was found hanging in jail in May 2013, before he could be convicted. Ram Singh was 35 years old at the time of his death.

The hangings bring to an end the long-delayed quest for justice in the Nirbhaya case. The Supreme Court had confirmed the death sentences for the accused in May 2017, but progress in the appeals process was slow, with the convicts filing curative pleas and mercy petitions individually since November last year.

A Delhi sessions court issued death warrants in the Nirbhaya case three times previously, but the hangings of the four convicts were deferred three times since January.

The Nirbhaya case had raised questions over legal statutes such as need to hang together multiple people accused of the same crime, but allowing them to avail of judicial recourse separately.