The rebel Liberation Tigers of Tamil Eelam (LTTE) blamed government forces for the killings as well as the disappearances from the Jaffna peninsula and the north-eastern areas where Tamils are concentrated.
"The worst affected district is Jaffna," the LTTE said, adding that some victims were killed by Sri Lankan military air strikes inside rebel-held territory.
The military denies targeting civilians and in turn blames the Tigers for using civilians as human shields as well as forcibly conscripting child soldiers.
International rights groups have said that about 1,000 civilians had been killed in the island in the past 20 months while another 1,000 had "disappeared."
The killings of civilians has increased since December 2005 with the escalation of fighting between troops and the Tiger rebels despite a truce arranged by peace broker Norway.
The Tigers are fighting to carve out an independent state in the tropical island's embattled northern and eastern regions.
The conflict has c