The UN secretary general is to press Sri Lanka for unrestricted access by aid agencies to civilians caught up in fighting against Tamil Tiger rebels, BBC reported.
Ban Ki-moon is the first senior world figure to arrive in Sri Lanka since the government said it had defeated the 26-year rebel insurgency this week.
About 275,000 Tamils are sheltering in camps in need of aid, but the army is still restricting access to the area.
Mr Ban is visiting an area in Vavuniya, where most of the displaced are held.
Aid groups have complained that their access to the displaced camps has been greatly restricted.
"There should be promotion and protection of human rights and there should be unimpeded access to the sites of the displaced by international, humanitarian organisations, including the United Nations," Mr Ban said when he arrived in the capital, Colombo.
Mr Ban said he would also appeal to the Sri Lankan President, Mahinda Rajapaksa, to resolve the long-standing grievances of the Tamil minority.
"It's time for Sri Lankans to heal the wounds and unite without regards for religious and ethnic identity," he said.
Without a political settlement that gives Tamils real rights, UN officials believe the fighting will begin anew, says the BBC's Laura Trevelyan in Colombo.
Senior UN officials acknowledge there is a risk that Mr Ban's visit could be used by the Sri Lankan govt to give international approval to its victory, our correspondent says.
Mr Ban told the BBC this would not happen, and that he was here to convey the concern of the international community.
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.