The rebel Liberation Tigers of Tamil Eelam (LTTE) said on its website that one more civilian was killed and five injured in Tuesday's shelling in the Vakarai area.
Earlier, the group said three people were killed and 11 hurt when a hospital in the same area was hit Monday.
The Sri Lankan military denied attacking civilians at the hospital, but said that troops have retaliated to guerrilla artillery attacks in the troubled region.
In another development in the island's northern Vavuniya district, two Tiger rebels -- a man and a woman -- were killed in a confrontation with troops on Tuesday, local officials said.
The incident came as the United Nations called on the combatants in the island's ethnic conflict to ensure civilian safety in battle zones.
"The United Nations calls for the protection of all civilians throughout the island," the statement said Monday.
The UN, while condemning alleged Tiger bombings that killed 21 bus passengers over the weekend, demanded protection f