The Red Cross evacuated hundreds of wounded people from the battle zone
The Sri Lankan government has told international relief agencies to cut back their activities in the country.
The government said the decision was taken because there was no more fighting, following the defeat of the Tamil Tigers rebels in May.
The International Red Cross (ICRC) says it is closing four offices in Sri Lanka's Eastern Province.
But it says an estimated 300,000 displaced people still need food, medicine and help to return home.
An ICRC spokeswoman in Colombo said the latest government decision did not affect its work at the Menik Farm camp complex in the north of the country, where more than 200,000 displaced Tamil civilians are detained.
The Sri Lankan authorities have been under pressure from aid agencies to relax official restrictions on access to camps where internally-displaced people are being held.
In the last months of fighting, tensions rose between the ICRC and the government over the fate of civilians. The ICRC spoke at the time of a "humanitarian catastrophe" but the government accused it of spreading panic.
Sri Lankan Human Rights Minister Mahinda Samarasinghe said the order was not only aimed at the ICRC.
"It is something we have told all international agencies. Since there is no more fighting now, we have told them and others that they should scale down their work. It is a decision we took after careful consideration," he said.
"The challenges are now different. Manning entry and exit points and handling dead bodies, transport of patients, in the post-conflict era are no longer needed."
The ICRC was the only outside agency with access to the area of combat in the final phase of the war, taking in aid and evacuating wounded people by ship.
Correspondents say that the latest announcement is significant because if the ICRC cuts back staff considerably, it could mean that eventually there is no independent monitoring of camps accommodating the displaced.
SRI LANKA CONFLICT TIMELINE
1976 - LTTE formed
1983 - First attacks by Tamil Tiger rebels; start of 'First Eelam War'
Feb 2002 - Government and rebels sign ceasefire
2004 - 2008 - Violence mounts
Jan 2008 - Government pulls out of ceasefire agreement
Jan 2009 - Government captures Tigers' Kilinochchi headquarters
May 2009 - Government declares victory against Tigers
The spokeswoman did not respond to an inquiry about whether the ICRC feels this is an appropriate time to cut back its operations in the country.
As a first step the ICRC said it was pulling staff out of the Eastern Province "while winding down operations in the area".
It said it had to respect the government's decision.
"Two sub-delegations are closing, Batticaloa and Trincomalee. A total of 140 national staff and about 10 expatriates worked in these offices," it said.
"The ICRC is in the process of reviewing its set-up and operational priorities in Sri Lanka," said Jacques de Maio, the organisation's head of operations for South Asia.
"However, the ICRC will continue its dialogue with the Sri Lankan government on issues of humanitarian concern."
The ICRC has had a permanent presence in Sri Lanka since 1989. It first began work in the southern part of the country, and continued in other parts as the conflict between government forces and the Tamil Tigers intensified.
Government troops defeated the rebels in mid-May after months of heavy fighting, and declared an end to the civil war which began in 1983.
Since the end of the military operation the ICRC has been helping co-ordinate relief for the displaced, and visiting rebel fighters who have been captured, to try to ensure that they are treated in custody in accordance with international law.