Karunanidhi, who arrived here today on a three-day visit, said he has been raising the issue with Singh now and then and will broach the topic again tomorrow.
"I have been discussing the fishermen issue with Singh on several occasions. I will raise the issue tomorrow also," he told reporters at the Tamil Nadu House here.
DMK sources said Karunanidhi will tell Singh that Sri Lanka should desist from firing at fishermen who allegedly cross the International Maritime Border and enter Lankan waters.
"He will ask the Prime Minister to tell Colombo to desist from firing at the fishermen. He will also tell Singh that India should convey its strong protest," the sources said.
She is expected to meet Foreign Minister G L Peiris and other senior Foreign Ministry officials and lodge India's strong protest over the issue.
Rao was asked by External Affairs Minister S M Krishna to travel to Colombo tomorrow to discuss with the Sri Lankan government the killing of Indian fishermen.
Reflecting the political sensitivities in Tamil Nadu, India has already reacted very strongly to the incidents in which two Indian fishermen were killed in the span of one month, notwithstanding Sri Lankan government's claim that its navy was not involved.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.