According to the defence ministry, clashes on Saturday and Sunday in the districts of Mannar, Vavuniya and Weli Oya left at least 100 rebels and five soldiers dead.
It said security forces kept up a major offensive against the Tigers and had taken more of the guerrillas' bunker lines.
The pro-rebel Puthinam.com website, however, said that the Tigers had killed 55 government troops and wounded another 120 in Saturday's fighting alone. The website did not give rebel casualties.
The government says it has killed 2,343 rebels since January against the loss of 136 of its own troops.
Colombo allows no journalists or rights groups into the embattled regions, making it impossible to independently verify the figures.
Thousands of people have been killed in a new wave of fighting since December 2005, when a Norwegian-brokered truce began to unravel. The truce was formally ended by the government in January.
The rebels have been battling for an independent homeland since 1972 in an et