A Sri Lankan army spokesman said that the fighting occured along a border that separated rebel-held terrain from government territory in the northern districts of Vavuniya, Jaffna, Polonnaruwa and the northwestern district of Mannar.
According to the Sri Lankan defence ministry, security forces had captured major locations from the rebels in the coastal district of Mannar over the past two days.
The fighting occured the same day when the rebels accused the military of blowing up a key rebel-backed parliamentarian, with a roadside bomb in northern Sri Lanka.
However, the military denied any hand in the attack.
Earlier, in January this year, the Sri Lankan government had scrapped a truce pact with the rebels, accusing them of using the ceasefire to re-arm themselves.
Three Sri Lankan members of parliament have also been killed this year, including the one on Thursday.
Mahinda Rajapaksa, Sri Lankan president, has taken a tough stand against the Tamil tigers and aims to defeat them by the end of this year.