Former Tamil National Alliance (TNA) parliamentarian Suresh Premachandran this week released pictures of the alleged torture camp in Vara'ni area of the district in which blood-stained walls of a house were shown.
Premachandran claimed the house was used as a cell by the Sri Lankan military to torture civil war detainees.
He said the chamber has been in existence since the army wrested Jaffna from the Liberation Tigers of Tamil Eelam (LTTE) in 1995.
"We had no reasons to maintain torture chambers and never heard of their existence", army spokesman Brigadier Jayanath Jayaweera said.
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Premachandran's revelations came a fortnight after a three-member team of the UN Working Group on Enforced or Involuntary Disappearances disclosed the existence of a similar camp in the eastern district of Trincomalee.
The secret Trincomalee 12-cell prison had markings on the walls that indicated detainees were kept there till 2010 -- one year after the nearly three-decade-long war against the LTTE ended, the UN group has said.
The UN has estimated that nearly 40,000 people were killed during the final phase of the bloody civil war in Sri Lanka.