Brigadere Prasad Samarasinghe, a military spokesman, said that the man was employed by the United Office Project Firm, and had been shot near his office in the eastern Ampara district on Thursday.
Samarasinghe blamed the Liberation Tigers of Tamil Eelam (LTTE), Sri Lanka's rebel movement, for the killing. The rebels have not yet commented.
The killing comes days after an ethnic Tamil Sri Lankan Red Cross worker was shot dead in the north on Sunday.
The 23-year-old woman was murdered by two men outside her home in Cheddikulam, Vavuniya, on August 20, according to the Sri Lankan Red Cross.
Also this month, 17 Sri Lankan workers for Paris-based aid group Action Against Hunger were shot dead in the northeastern town of Muttur.
Abuse of rights
Human Rights Watch has said that it is concerned about the soaring abuse of rights since the renewed violence broke out.
"It appears the LTTE was fighting with rockets in the vicinity of schools where there were displaced persons with a possible aim to protect themselves from military response"
James Ross, Human Rights Watch
James Ross, a senior legal adviser at Human Rights Watch, told Reuters on a visit to Sri Lanka: "Since the resumption of large-scale warfare, we have concerns about both sides failing to heed basic humanitarian law.
"There are specific instances we are looking into where it appears they might have used human shields.
"It appears the LTTE was fighting with rockets in the vicinity of schools where there were displaced persons with a possible aim to protect themselves from military response."
Recruitment of child soldiers by renegade rebels was a new worry in the war, according to Ross. The LTTE said that it has ceased the practice, but Ross said it was clearly continuing and condemned it.
The renegades, called the Karuna group, is a faction that has split from the main LTTE group.
Ross said: "The linkages between the Karuna group and the government ... seem to be very clear. In order for the Karuna group and others to abduct children in government areas they would have to go through government checkpoints."
Refugees, who fled heavy fighting in Muttur two weeks ago, told Aljazeera that young Muslim men - 16 to 19 years old - had been picked out of the crowd as they passed through LTTE checkpoints on the outskirts of the city. These refugees said that the young men were either shot dead or recruited to the LTTE.
Sri Lankan troops open a
checkpoint in Vavuniya
Residents of Muttur now living in the refugee camps in Kantale told Aljazeera that they have been regularly terrorised by the LTTE in the past into joining the rebel movement, and when they do not comply they are accused of being government informers.
Laying the blame
The government and LTTE frequently report atrocities by the other side, but almost invariably deny responsibility themselves.
Ross said: "Just because there is large-scale fighting going on, doesn't mean the problems we had before have gone away. There's a lot of blame to share around."
There are no firm figures for the number of civilians killed by fighting this month, but truce monitors say it is probably hundreds.
Ross said it was clear that neither side was taking steps to avoid civilian casualties.