Five men pleaded not guilty Saturday after being formally indicted in a special court on 13 charges, including rape and murder, in the fatal gang rape of a woman in a New Delhi bus, a lawyer said.

The men signed statements in the fast-track court saying they were innocent, said one of the men's lawyers. The lawyer cannot be identified under a gag order imposed by the court.

The court will begin hearing the evidence of witnesses on Tuesday.

A sixth suspect, who is 17 years old, will be tried in a juvenile court and could face a maximum sentence of three years in a reform facility if convicted. A conviction as an adult could have led to his execution.

Police say the victim and a male friend were attacked after boarding a bus Dec. 16 as they tried to return home after watching a movie.

The six suspects, the only occupants of the private bus, beat the man with a metal bar, raped the woman and used the bar to inflict massive internal injuries to her, police say.

The victims were dumped naked on the roadside, and the 23-year-old woman died from her injuries two weeks later in a Singapore hospital.

The brutal attack set off nationwide protests, sparking a debate about the treatment of women in India and highlighting the inability of law enforcement agencies to protect them.