Four men sentenced to death for a gang-rape and murder on a Delhi bus in 2012 that shocked the nation were given a week on Wednesday to exercise their remaining legal options.

Their brutal attack on Jyoti Singh sparked weeks of demonstrations, shining a spotlight on the dismal plight of women and alarming rates of sexual violence in 21st-century India.

The hangings have already been postponed twice and Delhi High Court judge Suresh Kumar Kait said that the men have played India's slow legal system long enough.

"It cannot be disputed that the convicts have frustrated the process by using delaying tactics," Kait observed, according to the Press Trust of India news agency.

He also said that they must be hanged at the same time as per the law, after the government applied for them to be executed separately.

The men were initially handed the death sentence in 2013.

A fifth, the suspected ringleader, was found dead in jail in a suspected suicide, while a 17-year-old accomplice spent three years in a juvenile detention centre.

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
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 AFP / SAM PANTHAKY

While two of the convicts have exercised their final legal options, the remaining two have yet to do so. Their options include pleas to the Supreme Court and mercy petitions to the president.

Another law stipulates that 14 days must pass after the president rejects a mercy plea before a person can be executed.

Wednesday's ruling comes amid widespread support for their execution within Indian society and among political parties.

The media has been full of gory details including that the nooses will be smeared with banana to soften them.

Singh, 23, was returning home from the cinema with a friend on a Sunday evening in December 2012 when they boarded a Delhi bus, thinking it would take them home.

The five men and one juvenile knocked the friend unconscious and dragged Singh to the back of the bus and raped and tortured her with a metal rod.

The physiotherapy student and the friend were then dumped on the road. Singh died 13 days later in a Singapore hospital from massive internal injuries.

India