One soldier died and two others were wounded Friday in a skirmish in Vavuniya district, a defense ministry official said on condition of anonymity, citing ministry regulations.
Hours later, soldiers killed four rebels during a confrontation in neighboring Mannar district, the official said.
Rebel spokesman Rasiah Ilanthirayan could not immediately be contacted for comment.
On Friday, the military said it had killed 19 other rebels in separate clashes in the north, also on Friday.
Each side in the conflict routinely exaggerates the other side's casualties, and plays down its own. Independent verification is difficult because the area is restricted to journalists.
The Tamil Tiger rebels have fought since 1983 to create an independent homeland for ethnic minority Tamils after decades of discrimination under governments controlled by the Sinhalese majority.
More than 70,000 people have been killed in the conflict.
The Chinese military believe that Beijing and Moscow must resist pressure from Washington together