UN Secretary-General Ban Ki-moon said his Saturday visit to Sri Lanka's largest refugee camp was "very moving," and he called on the government to allow aid groups greater access to hundreds of thousands of displaced civilians who need food and medical attention.

Upon his arrival in Sri Lanka, Ban visited the Manik Farm camp before flying over what used to be the battlefield for the rebels and government troops along the country's northeastern coast.

It was the first visit by an international figure since Sri Lankan President Mahinda Rajapaksa declared victory over the rebel Tamil Tigers on Monday, marking the end of a civil war that began in 1983.

After his tour of the camp, which houses some 200,000 people, Ban called it "a very sobering visit, very sad, very moving."

He said the camp does not have adequate sanitation facilities and lacks proper medical and food supplies.

Many of the refugees have serious injuries from having spent years living within a war zone.

"The situation, which I have seen for myself, is very, very difficult. It's a real challenge," Ban said. "There is clearly a limitation. The United Nations should try to fill this gap."

After meeting with Rajapaksa in the city of Kandy, Ban said the president promised that civilians would be resettled in their villages by the end of the year.

"We will try to work hard to make sure that promise is realized," he said.

From a helicopter, Ban got a view of burned-out, heavily cratered earth littered with overturned cars and trucks.

Human rights groups, as well as the rebels, accused the Sri Lankan government of spending the last several weeks firing heavy artillery in the war zone, where scores of civilians were trapped.

Aid groups estimate that about 300,000 civilians who were caught in the crossfire fled the area in recent months to government-run displacement camps, which are in desperate need of further supplies.

One civilian who identified himself as Krishnathurai told The Associated Press that those who fled the war zone were shelled by both sides during the conflict.

"It was coming from both sides, the Tamil Tigers and the military, and we were stuck in the middle," he said.

The Sri Lankan military has repeatedly denied that it shelled civilians.

The thousands that now reside at Manik Farm bathe in the open and are prevented from moving about by barbed wire fences.

Military officials have said they need to screen all displaced persons before allowing them to leave the camps in order to root out rebels from among the civilians.

Meanwhile, aid agencies accuse the government of allowing in only limited food and water supplies, despite a desperate need for medical provisions.

Chicken pox and various skin diseases are spreading rapidly, and hepatitis will soon become a problem due to poor sanitation, according to the aid group Oxfam.

Before arriving in Sri Lanka, Ban told reporters that he had three objectives, the first being "unimpeded access" for UN and humanitarian workers.

"I know that there are more than 300,000 displaced persons who are badly in need of humanitarian assistance -- food, water and sanitation," he said.

Ban said his second goal would be to help reunify families that have been torn apart by 25 years of civil war, as well as to reconcile the Tamil minority with the Sinhalese majority.

Tamils, which measure about 18 per cent of Sri Lanka's population, say they feel marginalized by the Sinhalese.

The Tamil Tigers had been fighting since 1983 to establish an independent Tamil state along Sri Lanka's northeast coast.

Tens of thousands of people died in the fighting.

"Now that the long decades of conflict are over, it is time for Sri Lankans to heal the wounds and unite without regards to ethnic and religious identity," Ban said upon his arrival in Sri Lanka.

Ban is expected to report findings from his trip to the UN Human Rights Council, which will meet Monday for a special session on Sri Lanka.

"I'll convey the concerns and aspirations and expectations of the international community to Sri Lankan leadership," Ban said. "Wherever there are serious violations of human rights as well as international humanitarian law, proper investigation should be instituted."

The UN estimates that at least 7,000 civilians were killed during the last few months of fighting.

With files from The Associated Press