Four men convicted of the 2012 gang-rape and murder of a New Delhi student will be executed on Friday, the victim's lawyer said after a court dismissed a final last-minute petition to delay the hangings.

The brutal attack on Jyoti Singh aboard a city bus sparked nationwide demonstrations and shone a spotlight on the alarming rates of sexual violence in India.

A trial court in Delhi, which had already postponed the hangings three times, on Thursday dismissed another plea to delay the executions scheduled for 5:30 am (0000 GMT) Friday.

"The court rejected their petition and said they have exhausted all their legal rights. The hangings will take place on Friday at the scheduled time," Singh's lawyer Seema Kushwaha told reporters.

Singh's mother Asha Devi welcomed the ruling and said her "daughter's soul will finally rest in peace".

The convicts had filed numerous petitions seeking delays to the executions.

One challenged the rejection of his mercy plea by the president, the last remedy available to death-row convicts in India.

The Supreme Court said it found no reason to interfere with the president's decision and rejected his petition.

The brutal attack aboard a Delhi bus sparked nationwide demonstrations and shone a spotlight on the alarming rates of sexual violence in India
The brutal attack aboard a Delhi bus sparked nationwide demonstrations and shone a spotlight on the alarming rates of sexual violence in India AFP / Prakash SINGH

Thursday's ruling came amid widespread support for the executions.

The media has also been full of grisly details about the hangings, including that the nooses will be smeared with banana and clarified butter to soften them.

Singh, 23, was returning home from the cinema in the evening with a friend when they boarded a 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.

The suspected ringleader was found dead in his prison cell in a suspected suicide, while the 17-year-old juvenile spent three years in a detention centre.

Almost 400 people are on death row in India, but no one has been executed since 2015.

India