Inmates in Dublin's maximum security Mountjoy Prison in Dublin poured boiling water laced with sugar down the throat of the man convicted for the killing of 16 year old Melanie McCarthy McNamara.

Keith Hall, who is currently serving a 20-year sentence for his role in the killing of the teenager in the west Dublin suburb of Tallaght last year, was reportedly rushed to hospital after the attack which happened in his cell last week.

When sugar is added to boiling water it forms a paste that adheres to skin and intensifies burns. It is a punishment tactic commonly used in prisons, where it is described as napalm due to the way it burns.

According to it was the second time in several weeks that Hall had been targeted by other inmates. In a previous incident a month ago he was stabbed repeatedly. Sources told the Journal that a bounty of $13,000 has been offered by people outside of the prison for any inmate who kills Hall. 'He’s afraid of his life,' the source reportedly said.

It's understood that Hall was released from hospital this week and has been moved to a solitary 23-hour lock-up in a bid to protect him from other inmates.

Hall, 24, was sentenced to 20 years in prison in July in connection with the killing of Melanie McCarthy McNamara, who was shot in the head as she sat in the back of a car in Tallaght in February 2012. Irish police said that the teenager was not believed to be the intended victim of the shooting.