COLOMBO, Sri Lanka (CNN) -- More than 100 Sri Lankan soldiers were killed and another 400 wounded Wednesday when troops attempted to advance toward a stronghold of the Tamil Tigers rebel organization, highly placed army sources told CNN.
Sri Lankan soldiers patrol the frontline on the Jaffna peninsula, the scene of fierce fighting.
The incident happened before dawn, when troops manning a defense line in the northern Sri Lanka village of Muhamalai attempted to advance toward the rebel stronghold of Kilinochchi in the northern Wanni region, the sources said.
The village is on a thin isthmus linking mainland Sri Lanka to the Jaffna peninsula. A defense line bordered by the Kilaly Lagoon on the west and the Indian Ocean on the east divides the rebel-controlled area from those held by the government's security forces.
Troops made an attempt to open a third front in the Wanni region by advancing south, Army officials said. Their ultimate aim was to reach Kilinochchi -- the power center of the Liberation Tigers of Tamil, better known as the Tamil Tigers.
"The rebels feigned they had withdrawn from their first line of defenses in well-dug-out trenches," one official said. "After the troops backed by battle tanks reached the area, the rebels sprung a fierce attack."
The incident deals a setback to military efforts to weaken the Tamil Tigers. Government leaders and military commanders vowed early this year to "eliminate" the rebels by the end of the year, but later extended the deadline into 2009.
Until Wednesday, the heavy fighting had remained focused in the western coastal town of Mannar and the northeastern coastal area of Weli Oya.
Local and foreign media are barred from visiting battlegrounds, except on conducted tours, and casualty counts from the military and the rebels are often exaggerated.
Initial information on the Wednesday incident came from the Media Centre for National Security, the only government agency disseminating information on the separatist war. In its latest update, it says 43 soldiers and more than 100 rebels have been killed, while 120 soldiers are injured and 33 are missing.
Independent verification of claims made by the center is often difficult.
The army sources also told CNN that at least 30 soldiers were reported missing in action. Rebel sources reported some soldiers remained lying on the battleground, but did not divulge a number.
Some of the injured were flown to Colombo hospitals. Officials appealed to the public on radio and television to donate blood. E-mail to a friend