Chennai, April 30 :     Three fishermen from Tamil Nadu were reportedly shot dead by the Sri Lankan navy, provoking an unusually sharp reaction from chief minister M. Karunanidhi who has sought the Centre's intervention. The fishermen from Nagapattinam on the eastern coast were fired upon by a 'nervous' Lankan naval patrol on April 23, state government sources said. Such incidents had happened earlier, but Karunanidhi's reaction has never been so high-pitched. He has written to the Prime Minister, demanding central intervention to end the sufferings of Tamil fishermen. He said the interests of the Tamil fishermen could not be sacrificed at the altar of harmonious relationship with Sri Lanka. 'The loss of any more lives will simply not be acceptable,' he added. The controversy has erupted a little over a week after Delhi was caught in a crossfire between Lanka and Vaiko, another ally of the BJP from the southern state. Lanka had officially protested against Vaiko's reported comments against President Chandrika Kuamaratunga at a human rights conference. Observers believe that Karunanidhi's tough stand could be because the Assembly elections are hardly a year away and he would not like to provide ADMK general secretary Jayalalitha with a campaign plank. Jayalalitha today condemned the incident, and alleged that it had occurred due to the Indian navy's 'lethargic' attitude. Though more often than not, it is the Rameswaram fishermen who stray into the Lankan waters in search of prawns in the Kacha Theevu region, fishermen of other areas too, cross the borders. Even the Lankan Tamil fishermen do this occasionally. But the ethnic bloodbath of Tamils in Colombo and elsewhere in 1983 and the consequent Tamil uprising has changed all that. With increasing militant traffic between the Indian shores and the Tamil areas of Sri Lanka, any boat found in the international waters became suspect in the eyes of the Lankan navy. The situation deteriorated further when the Tamil Tigers emerged as a formidable force. Fishing boats were fired upon and sunk, fishermen, abducted and kept in detention camps and sometimes shot dead. With the Lankan military driven to the wall at the moment, the Lankan navy has apparently become edgier.