Sri Lankan troops and Tamil Tiger rebels were locked in heavy combat across their de facto borders in the north of the island where at least 36 combatants were killed, the defence ministry said on Wednesday.
Intense clashes along the Mannar and vavuniya districts left 20 guerrillas and three soldiers killed on Tuesday, the ministry said adding that another 12 guerrillas and a soldier were killed further north in the Jaffna peninsula.
The rebel Liberation Tigers of Tamil Eelam (LTTE) denied ministry claims and said they killed 26 government soldiers for the loss of only three of their own men in Tuesday's fighting.
The latest defence ministry figures bring to at least 248 the number of guerrillas it has claimed to have killed since the beginning of the month. Only a handful of government soldiers have been reported killed or injured in the same period.
No independent confirmation of the casualty claims were available, and journalists are barred from frontline areas.
The London-based Amnesty International and New York-based Human Rights Watch have repeated calls for a UN rights monitoring mission in Sri Lanka, where fighting between troops and Tamil rebels has surged since December 2005.
Since September, more than 20,000 people have been displaced by the fighting, according to rights groups.
Sri Lanka has strongly resisted calls for a UN monitoring mission in the country, where more than 60,000 people have been killed in the ethnic conflict since 1972.