NEW DELHI: A defendant on trial over a fatal gang-rape of a student on a bus in India last December is in a “very critical” condition after being attacked by fellow prisoners, his lawyer said Wednesday.

Vinay Sharma was rushed to the state-run Lok Nayak Hospital in New Delhi on Tuesday with chest injuries after he was assaulted in Tihar Jail, lawyer A. P. Singh told AFP, also alleging that his client's food had been poisoned.

“He was vomiting blood and running a very high fever. He was also suffering from chest pains. He is in a very critical condition,” Singh said.

The chest pains came after Sharma, 20, was “beaten up and thrashed” by fellow inmates at the maximum-security jail, the lawyer added.

The vomiting was the result of the “slow poisoning” of his food over a period of several weeks, said the lawyer.

One of Sharma's co-defendants, bus driver Ram Singh, was found hanged in his cell in the same prison in March.

Sharma is one of four adults on trial for murder, gang-rape and robbery in connection with the December 16 attack on a bus. The 23-year-old student died of her injuries in a Singapore hospital 13 days later.

A fifth defendant, who is aged 17, is being tried in a juvenile court.

The head of the hospital refused to comment on the case while there was no immediate reaction from authorities at Tihar.