Pawan Kumar feels zero sympathy for the four men he is due to hang next month for the 2012 gang-rape and murder that appalled India.

"The people who are going to die are like beasts, not humans," the third-generation hangman said.

"They are cruel people and that's why they are going to lose their lives," the 54-year-old said.

The group set to be executed at 6 am on February 1 were convicted for the gang-rape and murder of a 23-year-old student.

They took turns to sexually assault her and brutalised her with an iron rod on a bus as it meandered through the streets of Delhi at night. They then dumped her on a road.

She died two weeks later in a Singapore hospital from extensive internal injuries.