Vijay Nambiar, chief of staff of UN Secretary General Ban Ki-moon, visited camps around Vavuniya that are housing some 130,000 people displaced by the war in the northern part of the island, according to the UN press office.
His visit came a day ahead of Ban's scheduled arrival in Sri Lanka.
The Sri Lankan government earlier this week claimed victory over the Liberation Tigers of Tamil Eelam (LTTE), ending its three-decade-old insurgency for a Tamil homeland.
The International Committee of the Red Cross (ICRC) earlier Thursday deplored the decision of the Sri Lankan government to restrict the flow of humanitarian aid to the biggest refugee camp, Menik Farm, near Vavuniya.
Sri Lanka has said it plans to re-settle most of the 250,000 Tamils displaced by the war within six months, according to two Indian envoys who met with President Mahinda Rajapakse.
The United States also Thursday urged the Sri Lankan government to lift restrictions on access to refugee camps.
"We urge