Tamil Tigers have condemned a statement by Sri Lanka ceasefire monitors saying the rebels have no rights at sea.
The Tigers say they have a right to operate at sea
The rebels and monitors held emergency talks in the wake of a sea battle which the government says left dozens dead.
After the incident, the monitors blamed the Tigers for provoking the navy, saying it was "very clear that the Sea Tigers have no rights at sea".
Rebel official SP Thamilselvan said the Tigers had asked the monitors to explain their statement.
The government says 17 troops and more than 40 rebels died in a Tiger suicide sea attack near Jaffna on Thursday. The Tigers say the navy attacked them and say only four of their members were killed.
The head of the SLMM monitoring force, Major-General Ulf Henricsson, held the emergency talks with Mr Thamilselvan, leader of the group's political wing, in the northern town of Kilinochchi.
The BBC's Dumeetha Luthra says the talks were not to resolve the issues or get peace talks back on track, but to send a clear message from the monitors to the Tigers that the attack on the navy was a serious violation of the ceasefire.
Afterwards, Maj-Gen Henricsson described the meeting as cordial.
Mr Thamilselvan said he had conveyed the Tigers' "disappointment and objection" to the earlier statement about rights.
"Nobody has the right to pass judgment on the sovereign rights of our access to the adjacent sea and air space of our homeland," a Tamil website quoted him as saying.
In an earlier letter to the monitors, he also urged them "for the last time" not to board navy vessels. A monitor was on one of the navy ships involved in Thursday's incident.
Separately, the monitors say they suspect the Sri Lankan authorities are involved in extra-judicial killings of Tamils, although not in a systematic way.
Robert Nilsson, a spokesman for the SLMM, told the BBC's Newshour programme that the rebels had a right of access to the waters of northern Sri Lanka.
"There is an understanding for them to exercise at sea, and there have been some sea movements, transporting cadres from leave, but that doesn't justify yesterday's attack," he said.
Violence has soared in Sri Lanka in the last month, leaving about 200 people dead.
More than 60,000 people have been killed in the country since the Tigers launched their campaign for a separate state in the north and east of the country in 1983.