The bomb had been planted on a three-wheeler parked near the checkpoint at the entrance of the town by suspected Tamil Tiger rebels, a police spokesperson said. The spokesperson said at least 12 people were hospitalised with injuries while many more were treated for minor wounds and sent home.
Military officials initially thought the blast had been caused by a grenade attack, but later tracked it down to the three-wheeler.
The attack came hours after a similar bombing in the eastern district of Batticaloa where four policemen were wounded. Though largely controlled by government forces, Trincomlee and Batticaloa districts have pockets dominated by LTTE and its breakaway faction.
The latest attacks come amid sporadic clashes between government troops and Tamil Tigers despite a truce that is in place since February 2002.