The rebel Liberation Tigers of Tamil Eelam (LTTE) pounded the Muhamalai defence line in the Jaffna peninsula in a pre-dawn assault, a defence ministry official said.
They said several other attacks by the rebels were also reported elsewhere in the island's east.
The latest violence came a day after the Colombo government vowed to keep up an offensive against the Tigers until they stopped "provocative actions."
President Mahinda Rajapakse promised to retaliate against rebel attacks when he sought the support of Sri Lanka's main international donors for efforts to coax the rebels back to the negotiating table.
Diplomats from the United States, the European Union, Japan and Norway held talks here Monday with Rajapakse on peace broker Oslo's latest bid to arrange peace talks later this month.
The government and the Tigers have agreed to talks aimed at ending three decades of ethnic bloodshed, but they have yet to finalise a venue and an agenda.
Some 60,000 people have been killed in the s