Brigadier Prasad Samarasinghe, a Sri Lankan army spokesman, said on Sunday; "We have suffered 28 killed and 119 injured. Troops are consolidating this morning."
Samarasinghe said about 130 Liberation Tigers of Tamil Eelam (LTTE) fighter may have been killed, but the figure was unconfirmed.
The army blames the LTTE for starting the latest round of fighting by shelling their frontline positions in the Muhamalai area of the northern Jaffna peninsula.
The military responded with artillery and air strikes before advancing around 600m across the heavily mined frontline on Friday to capture Tiger bunkers.
"It's not about capturing land, it's only the neutralising of their frontline," Samarasinghe said.
'Declaration of war'
The army captured a Tiger stronghold on Monday near the strategic Trincomalee harbour in the northeast of the island after days of artillery battles.
On Friday, senior Tiger leader S Puleedevan told Reuters the seizure of Sampur, the first major capture of territory by either side since the ceasefire was signed, was "tantamount to a declaration of war".
The Tigers' political chief, SP Thamilselvan, said it had brought an end to the ceasefire agreement.
But the government says it was forced to take Sampur because the insurgents had been using it to shell a naval base in Trincomalee and disrupt a maritime supply route to the besieged, army-held Jaffna peninsula.
Hundreds of civilians, troops and Tiger fighters have been killed since Sri Lanka's two-decade civil war re-erupted in late July, and more than 200,000 people have fled to refugee camps across the island's rural northeast.