Tirunelveli, Oct 12: The Central Prison here has received a letter, from a person claiming to be belonging to the 'Coimbatore unit of Al-Qaeda', which states that it would be attacked shortly, officials said.
The anonymous writer said he was protesting against the unfair treatment meted out to the prison inmates, they said.
The officials said the prison was strongly protected and security had been further tightened. The letter was sent from Coimbatore.
The Central Prison at Coimbatore had recently received a threatening letter allegedly from Al-Qaeda, which was sent through an outfit identified as 'The Base Movement'.