India has lodged strong protest with the Sri Lankan government over the recent incidents of firing by the island nation's navy on Indian fishermen, a senior Coast Guard official said on Monday.

The recurring incidents of Sri Lankan Navy firing on Indian fishermen were of serious concern and this had been brought to the notice of the island's republic government, Coast Guard Director General Vice-Admiral R F Contractor said.

"The Sri Lankan Navy looks for suspicious vessels, especially in the night, and has been firing indiscriminately, for security reasons. Several of our fishermen, who have been straying into foreign waters due to lack of navigational equipment, have been hurt in the firing," he said.

He attributed the reason for the frequent problems between the Sri Lankan navy and Indian fishermen, mostly from Tamil Nadu, to the large number of unregistered boats fishing in Indian waters.

"Though as many as 1,65,350 boats have been registered, there are even more unregistered boats, which are into fishing operations illegally. Thus, it is posing a huge challenge to the Sri Lankan Navy to differentiate between genuine fishermen and extremists and others," Contractor said.

With the inflow of Sri Lankan refugees hitting an all time high of over 13,600 this year, compared to over 34,600 in the past decade, the Sri Lankan and Indian Navy had stepped up vigil in the International Maritime Boundary and were undertaking co-ordinated patrolling of international waters, he said.

The Coast Guard was taking all steps to combat smuggling and poaching in the south of Sri Lanka [Images], as the shipping activity increased, and the maritime boundaries of Bangladesh, Contractor said.

The Sri Lankan government sought the assistance of the Indian Coast Guard in controlling the oil leak caused due to the sinking of a Bangladeshi ship in Sri Lankan waters last week, and they were very happy with the work done by our pollution buster vessels, he said.

"As part of its vision, the Indian Coast Guard will acquire as many as 200 offshore patrol vessels, small interceptor boats and other vessels, including six multi-mission aircraft," he said.

With the delineation of the maritime boundaries, the maritime area covered by India, which is around 2 million sq km at present, was expected to go up to over 3 million sq km, he said.

"Even with 44 ships and seven aircraft with the Eastern Regional Command at present, we are able to cover only 40 per cent of the coastal area," Inspector General Rajender Singh, Commander, Coast Guard Region, East, said.

"The induction of more number of ships into the Coast Guard fleet, will help fill in these gaps," he said.