The soldiers were killed when a bomb exploded on Saturday morning as they cleared the Muhamalai on the northern peninsula where 11 days of battles have left some 650 Tigers and soldiers dead.
A military source from Jaffna said 11 other soldiers were wounded when a bomb went off as troops were on an operation clearing bunker lines.
The peninsula remained relatively calm overnight after the arrival of the first shipment of aid for the tens of thousands of people who have fled fighting in the area.
Jaffna is largely held by the government but is cut off by road from the rest of Sri Lanka by separatist forces.
Meanwhile the Tigers released a policeman held for over 10 months in northern Sri Lanka as a "goodwill gesture", monitors of the country's failing ceasefire said.
BW Bopetigoda, was handed over to monitors during a ceremony on Saturday morning, Thorfinnur Omarsson, a spokesman for the Nordic mission, said.
Bopetigoda was one of three officers arrested by separatists in Tiger-held territory in the north in September 2005. Two other officers had already been released.