Tamil Nadu Chief Minister M Karunanidhi on Friday received a death threat allegedly from the banned LTTE, police said.
Police said a letter carrying the symbol of the proscribed outfit issuing the death threat was received at Karunanidhi's Gopalpuram residence.
Following the threat, security has been stepped up for the Chief Minister, who already is in the 'Z plus' category.
A case has been filed with the Central crime branch of the city police which is probing the matter.
Police officials said the Union Home Ministry had already warned of a terror threat to Karunanidhi from LTTE, which is engaged in what is been termed as the "last ditch battle" in Sri Lanka.