WASHINGTON - A Pakistani high school honours student who reportedly helped solicit support for jihadists he met online was sentenced to five years in prison in Philadelphia on Thursday, according to US media reports.

Mohammad Hassan Khalid, the youngest person ever to be prosecuted for terrorism offences in the US, had earned a full scholarship to Johns Hopkins University, an elite educational institution, after just a few years in the United States, where his family immigrated from Pakistan.

As his parents and siblings worked hard to make a living, he retreated to his bedroom in the family's apartment near Baltimore and joined radical Islamist chat rooms by the time he was 15. He was soon conversing with Coleen LaRose, a Pennsylvania woman who called herself “Jihad Jane,” and other extremists. LaRose, who is serving a 10-year prison sentence for her part in the conspiracy, allegedly drew him into a plan to kill the Swedish artist Lars Vilks, who had drawn a caricature of the Prophet Muhammad (Peace be Upon Him).

“The upheavals of my life were distorted into a force of hate so strong that it wrapped me in its claws,” Khalid, now 20, told Judge Petrese Tucker. He said he had trouble speaking without being misunderstood.  Khalid, a Pakistani citizen and legal permanent resident in the US, lived in Ellicott City, Maryland, with his immigrant family before his arrest in July 2011.

He said: "I stand before your honour humiliated." He spoke of pain, anguish and upheavals in his life. "Nothing I say today can excuse the mistakes of my past." He asked for his parents' forgiveness and the judge's mercy. His older brother, who sat in the gallery with their parents and his two sisters, cried. Khalid has already spent almost three years behind bars and will get credit for time served. Because he is not a US citizen, he is expected to face deportation and could be sent back to Pakistan after he serves his sentence.

"What (Khalid) did, bad as it was, was not this international jihad the government keeps talking about," defence attorney Jeffrey Lindy told the judge.

Lindy argued that Khalid was isolated and vulnerable because he was a young immigrant and had an autism spectrum disorder diagnosed since his arrest. Prosecutors say Khalid used his “brilliance and eloquence,” along with his computer skills, to help radicals translate documents and try to recruit westerners. That got the attention of the FBI, which visited Khalid repeatedly.

“The FBI tried very sincerely to talk him out of his criminal conduct because of his youth. He wasn't interested,” Assistant US Attorney Jennifer Arbittier Williams argued. “It was his persistent desire to be an online hero in the world of jihad” that got him into trouble, she said.

Since his 2011 arrest, Khalid has given significant help to US officials pursuing various Al-Qaeda offshoots, assistance that took years off his potential sentence of 15 years for providing material aid to terrorists.

“Coleen LaRose had as much chance of killing Lars Vilks as I did. No chance,” Khalid's defence lawyer, Lindy, argued on Thursday. He called the plot, which never led to an attack, “half-baked,” and said Khalid's role fell far short of criminal conspiracy.