Heavy fighting broke out across Sri Lanka's northern area of Kilinochchi, leaving 37 Tamil Tiger rebels and six soldiers dead, the defence ministry said Wednesday.
It said 34 rebels and 25 soldiers were also wounded in the fierce fighting that took place on several fronts on Tuesday.
The Liberation Tigers of Tamil Eelam (LTTE), who are battling a government push to dismantle their northern mini-state, did not comment on the military casualty claims.
Sri Lankan troops say they are just two kilometres (1.2 miles) from Kilinochchi, which has been the LTTE's administration centre for the past decade.
Troops have killed 7,553 rebels since Sri Lanka pulled out of a Norwegian-backed truce in January, while 748 soldiers died in combat, according to a defence ministry toll. The figures cannot be independently verified.