Security forces have been trying to push into territory held by the Liberation Tigers of Tamil Eelam in the past week amid intense resistance by the guerrillas, official sources said.
"As the rains set in by October, it will be difficult to use artillery and tanks," a military official said.
"Before the monsoon breaks there will be increased skirmishes along the front lines."
Government figures show over 45 guerrillas have been killed in the past week while the military lost six troopers, as both sides intensified artillery and mortar bomb attacks across their defence lines.
Few casualties were reported by both sides in the previous week.
In the northern peninsula of Jaffna, a road side blast Thursday killed two civilians and wounded another 15 people, including two policemen, the defence ministry said, accusing the Tigers of setting off the blast.
In the island's northwest, a Roman Catholic priest was killed when his vehicle was hit by a blast on Wednesday. The Tigers accus