The Intelligence Bureau (IB) has issued a fresh alert over the suspected jihadi links of the youngest Nirbhaya rapist, who was released in December because he was a minor at the time of the fatal Delhi gang-rape.

Authorities in Uttar Pradesh have been advised to keep a close watch on his movements as the man, now 21, hails from the state’s Badaun district.

He ended his three-year term in a reform home six months ago, after being found guilty along with five others of the brutal attack on a 23-year-old woman, dubbed Nirbhaya, in a case that prompted nationwide revulsion and turned the global spotlight on crimes against women in India.

The youngest convict in the Nirbhaya case was released in December last year, after serving a three-year sentence in a juvenile reform home. Now intelligence sources fear he was radicalised by his cellmate.

“Recently some activity was noticed and we informed the local authorities,” said an intelligence official, without saying anything about the man’s present whereabouts.

Before his release in December 2015, the IB raised fears about his closeness to a Kashmiri inmate at the juvenile home, who was involved in the 2011 Delhi high court bombing.

The two shared the same room for over a year, and it is alleged that the rapist's cellmate indoctrinated him and prompted him to take up the cause of Kashmiris.

“There is no specific input but whatever assistance is required will be provided by us,” said Sunil Saxena, senior superintendent of police, Badaun.

Hundreds of people, including Nirbhaya’s parents, had staged protests in the Capital against the convict’s release, with the campaign spurring Parliament to pass legislation lowering to 16 the age at which someone can be tried for serious crimes.

The youth's radicalisation was also pitched as one of the reasons to stop his release. The convict himself expressed fears that he might be lynched once he was set free.

BJP leader Subramanian Swamy also approached the Delhi high court, but the judges rejected his plea saying the sentence complied with existing law.

"Having regard to the fact that the maximum stay that can be directed in the Special Home under Section 15(1) of the Juvenile Justice Act is three years and that the convict would be completing the period of three years by December 20, 2015, there cannot be any direction to continue his stay in the special home beyond December 20. Hence, we decline to issue any direction as prayed by the petitioner," the bench said while allowing the convict to walk free.

In its report prior to his release last year, the Intelligence Bureau said the Kashmiri youth had brainwashed his cellmate and motivated him to join jihad in Kashmir.

As per the instructions of the union home ministry, the rape convict went through counselling sessions for de-radicalisation.

A trial court awarded the death penalty to the four adult accused in the Nirbhaya gang-rape case for the gruesome act.

The woman was sexually assaulted on a moving bus and horrific serious internal injuries after being penetrated with an iron bar during the attack.