However, the LTTE rejected the claims, saying they did not suffer any deaths and that they had thwarted military attempts to break into their territory.
The Tigers said in a statement that they also killed one government soldier in Thursday's battles.
The latest casualty claims by the military bring the number of Tamil fighters killed since December 1 to at least 501, according to the defence ministry.
This compares with less than 30 troops reported dead or missing by the military.
Both sides regularly make sharply differing claims about casualties and independent verification is rarely possible. Journalists are also not allowed access into rebel held areas in the north. Sri Lanka is pressing for a military victory over the rebels, fighting for a separate state for the ethnic Tamil minority in the Sinhale