The government denied earlier on Wednesday launching an offensive against the Tigers, saying the military action was in retaliation for attacks on its troops.
Security forces along the forward defence line near Muhamalai had been "forced to retaliate" to sporadic attacks by rebels since late Tuesday, using heavy artillery and rockets, the Media Centre for National Security said.
It said the air force and navy had helped "neutralise and destroy identified Tiger concentrations and reinforcements by the sea."
The fighting killed 22 soldiers and a "large number" of Tigers and 113 more troops were wounded.
Rasiah Ilanthiraiyan, a Tamil Tiger military spokesman, said: "The military is staging a full-scale offensive along our northern border.
"They have come as far as our positions, but they haven't breached them. They are firing the biggest of their guns."
The Tigers said at the weekend that the military was preparing to mount a fresh onslaught and repeatedly said that any incursion into territory held by them would mean the end of peace negotiations.
"It is crucial that the government and the LTTE now use this opportunity to cease hostilities"
Erik Solheim, Norwegian peace negotiator
The Tamil Tigers released a statement saying: "The attacks come hot on the heels of repeated warnings by LTTE [Liberation Tigers of Tamil Eelam] political head, SP Thamilselvan, to the Norwegian facilitators and the international community to ensure that such large scale attacks are halted in view of the proposed direct talks."
The Tamil Tigers had agreed on Tuesday to resume peace talks which are due to take place in Geneva on October 28 and 29.
Thamilselvan said in a statement posted on their official website: "We are ready for talks, and agreed to the venue and date."
But he later told the pro-Tiger Tamil.net website: "However, if the military aggression continues, we will be forced to reconsider the decision."
Erik Solheim, Norway's top peace negotiator, had welcomed on Tuesday the agreement between the Sri Lankan administration and the Tigers to hold talks.
Solheim said: "It is crucial that the government and the LTTE now use this opportunity to cease hostilities.
"They are taking a small but important step towards continuing the peace process although the situation on the ground remains difficult."