Sri Lanka's troops finally ended the war at the weekend
Sri Lanka says more than 6,200 security personnel were killed and almost 30,000 wounded in the final three years of the war with the Tamil Tigers.
Defence Secretary Gotabaya Rajapaksa revealed the figures on state TV - the first such official statement.
It is thought at least 80,000 people have been killed in the 26-year war.
UN Secretary General Ban Ki-moon arrived in Sri Lanka on Friday to discuss the plight of about 275,000 internally displaced people.
Sri Lanka officially announced an end to the war this week, after its troops took the last segment of land held by the rebels, and said it had killed the top Tamil Tiger leadership, including its chief, Velupillai Prabhakaran.
Mr Rajapaksa, brother of President Mahinda Rajapaksa, told the state-run Independent Television Network the final phase of the operation against the rebels had begun in August 2006.
"Since then the security forces, including the army, navy, the air force, police and the civil defence force, have lost 6,261 personnel killed and 29,551 wounded," Mr Rajapaksa said.
"We made huge sacrifices for this victory."
There are no official figures for the number of Tamil Tiger rebels killed in the civil war, although estimates vary from between 15,000 and more than 22,000.
The UN says 7,000 civilians have died since January alone, although the government disputes this figure.
The focus will now shift to the resettlement of the internally displaced.
On Thursday, two visiting Indian envoys met the president and said they had been told Sri Lanka would resettle most of the displaced Tamils within six months.
The issue will be top of Mr Ban's agenda.
Camps in Vavuniya will be visited by the UN's Ban Ki-moon
Aid groups complain their access to the displaced camps has been greatly restricted.
Mr Ban will visit the Manik Farm area in Vavuniya, where most of the displaced are held.
He has sent his own envoy, Vijay Nambiar, ahead of him and on Friday Mr Nambiar said there had to be a political reconciliation.
"The process of national reconciliation, we feel, must be all inclusive so that it can fully address the legitimate aspirations of the Tamils as well as other minorities," he said.
"It is important that victory becomes a victory for all Sri Lankans."
Mr Nambiar said he had flown over the conflict zone to assess it.
"We were not able to see any civilians. What was truly striking was the almost total absence of human habitation... it was almost eerie."
He would also not rule out possible investigation of war crimes.
"Where there are grave and systematic violations of international humanitarian law, these are things which should be looked at by the international community, by the United Nations," Mr Nambiar said.