Five men accused of the savage gang-rape and murder of an Indian student pleaded not guilty on Saturday in a case that shocked the nation and sparked huge demonstrations, one of their lawyers said.

The 23-year-old physiotherapy student was brutally assaulted in mid-December on a New Delhi bus she had boarded with a male companion as they returned home from watching a film.

The trial of the five men on charges that include murder, gang-rape and kidnapping is being held in a fast-track court in Delhi set up to deliver speedy justice following public anger over the case.

A sixth suspect faces trial in a juvenile court.

"All five have pleaded not guilty and want the trial to continue," defence lawyer V.K. Anand told AFP outside the court.

The five men were surrounded by heavy security and rushed into the court building, their faces concealed with scarves. They remained in the courtroom for around 10 minutes before being escorted out.

The court will start hearing evidence in the case from witnesses next Tuesday, the lawyer said.

The case sparked violent street protests with demonstrators demanding better safety for women and making impassioned calls for harsher laws to punish rapists.