Marumalarchi Dravida Munnetra Kazhagam chief Vaiko and his supporters on Monday sat on a day-long fast to protest against the visit of Sri Lankan President Mahinda Rajapakse.
Rajapakse is seeking naval assistance from India to curb the influx of arms into the island nation.
Besides Vaiko, MDMK MPs S Ganesh and N Ramachandran and other party leaders also took part in the hunger strike at Jantar Mantar in New Delhi demanding that India reject any Lankan proposal for defence assistance.
"The Sri Lankan President is cunningly trying to make a trap to get India's naval assistance for their military offensive [against the Liberation Tigers of Tamil Eelam]. India should totally reject such a proposal if it is placed by Sri Lanka," Vaiko said, addressing his supporters.
In a memorandum to External Affairs Minister Pranab Mukherjee, he said India should make efforts to prevail on the Sri Lankan government to open Highway A-9 to remove an economic blockade and military attacks against Tamils.
Former Jammu and Kashmir Chief Minister Farooq Abdullah and Akali Dal leader Sukhdev Singh Dhindsa visited Vaiko to express solidarity with his cause.