Arthur Max - Sri Lanka's president Sunday rejected a call by the United Nations secretary general to lift restrictions on aid delivery to overcrowded displacement camps, saying the army must first finish screening the hundreds of thousands of Tamil refugees.

President Mahinda Rajapaksa's statement came in response to an appeal by Ban Ki-moon during a 24-hour visit to Sri Lanka for unfettered access for aid agencies to the camps, where nearly 300,000 Tamils were herded during the final stages of the war against Tamil Tiger rebels.

The government proclaimed victory last week in the 25-year insurgency by the rebels, formally called the Liberation Tigers of Tamil Eelam, who sought to create an independent Tamil country in Sri Lanka's north and east.

Ban's hurried visit was intended to press the government to ease what aid agencies described as a humanitarian crisis in the camps, with inadequate food supplies and reports of epidemics because of improper sanitation.

But Rajapaksa said security had to be assured "in view of the likely presence of LTTE infiltrators" among the refugees. "As conditions improved, especially with regard to security, there would be no objections to such assistance, from organizations that were genuinely interested in the well being" of the displaced Tamils, he said.

The wording appeared to reflect widespread mistrust among many Sri Lankans who believe some humanitarian agencies have a pro-Tamil political agenda.

The bluntness of the president's statement contrasted with the milder tone of a joint communique with Ban, released almost simultaneously.

In that statement, Ban said the UN would continue providing humanitarian assistance to the displaced people, and Rajapaksa promised to "continue to provide access to humanitarian agencies."

After visiting the barbed wire-enclosed Manik Farm camp Saturday, Ban described conditions as "very, very difficult. It's a real challenge." He said the government lacked the resources to deal with the problem, but that the UN could fill the gaps.

"It was a very sobering visit, very sad, very moving," he said.

Civilians told Ban they had escaped the war zone after coming under intense shelling from both the rebels and the government.

"We ran for our lives from the shelling in the north," said one man who gave his name as Krishnathurai. "It was coming from both sides, the Tamil Tigers and the military, and we were stuck in the middle."

Ban then flew over the former battle ground to see for himself, and saw a wasteland of scorched earth, shell craters and burned-out vehicles and tent camps.

The government has denied firing heavy weapons into an area that had been densely populated with civilians who had been kept their against their will by the rebels. But the helicopter tour given by the military to Ban and a group of journalists revealed widespread devastation.

In the joint statement, the government pledged to rebuild democracy in territory recaptured from the rebels and to reintegrate child soldiers conscripted into the rebel army.

Until the latest army offensive, the Tamil Tigers had run a de facto government in roughly one-third of the island, with their own police force, courts, tax system and bureaucracy.