The Sri Lankan army says it captured four Tamil Tiger bases and killed 23 rebels in clashes in the east of the island overnight.
The Tigers are fighting for an independent Tamil homeland
The fighting took place in the district of Batticaloa, military spokesman Brig Prasad Samarasinghe said.
There has been no comment from the Tamil Tigers.
Some 4,000 people have been killed in escalating violence since late 2005, with tens of thousands of civilians being displaced.
"There are 23 confirmed LTTE (Tamil Tigers) dead," military spokesman Brig Samarasinghe told journalists in the capital, Colombo.
"We have captured four bases without confrontation."
The army's reported capture of the bases in Batticaloa comes hours after a deadly bomb attack on a civilian bus in Ampara district further south along the coast.
At least 16 people were killed in the attack. The army blamed the Tigers for the blast, the Tigers denied responsibility.
Eastern Sri Lanka has seen the heaviest fighting in recent months with the military making a number of advances into Tamil Tiger territory.
On Monday a bomb on a civilian bus left 16 people dead
Human rights groups have expressed grave concern for the plight of displaced civilians and the United Nations has warned of impending food shortages for the homeless.
Both the Tigers and the military are, officially, still observing a 2002 ceasefire which has become meaningless in practice.
Violence began to increase after the 2005 election of President Mahinda Rajapakse.
The Tigers are fighting for a Tamil homeland in the north and east of the island.