At least 13 people were injured as heavy fighting broke out in Sri Lanka's [Images] restive northeastern district of Trincomalee with troops and Tamil Tiger rebels trading long-range attacks.

Military sources said at least 13 soldiers were wounded in artillery attacks carried out by the Liberation Tigers of Tamil Eelam in the district of Trincomalee.

For their part, the Tigers said it was the military, which launched the offensive and had wounded 13 people sheltering at a school building.

The military had closed some of the roads in the area as artillery attacks escalated, local officials said.

The renewed attacks came as peace broker Norway failed on Friday to secure an agreement to end a blockade on the Jaffna peninsula where nearly half a million people are trapped by fighting.