NEW DELHI: Defence lawyers began cross-examining Wednesday the male companion of a student who was gang-raped on a bus in New Delhi at the trial of five adults accused of her murder, the man's father said.

"The cross-examination has begun," said the father of the 28-year-old IT specialist, who cannot be named for legal reasons.

"Three defence lawyers will cross-examine and question him based on the statement that he gave to the police and the court," he added.

The cross-examination comes after the companion, who is the chief prosecution witness, had on Tuesday identified the bus on which the fatal attack took place on December 16. The bus had been brought to the court compound.

The five adult defendants have all denied murder, rape and robbery charges for which they are being tried at a special fast-track court in the Saket district of the Indian capital.

A sixth defendant is being tried separately as a juvenile.

The 23-year-old medical student died in a Singapore hospital on December 29 from massive internal injuries she sustained during the savage bus assault a fortnight earlier, which caused outrage across India.

She and her companion had spent the evening at the cinema and were lured onto the off-duty bus after failing to flag down an autorickshaw to take them home.

As well as taking turns to rape the woman and violating her with a rusty iron bar, the group attacked her companion so badly that he is still unable to walk properly. He again appeared at the court on Wednesday in a wheelchair.

The judge has banned all reporting of proceedings inside the courtroom and ordered lawyers not to speak to journalists.