Monks led about 300 protesters from the Buddhist nationalist National Heritage Party, which is a Sri Lankan ally, during the demonstration opposite a local U.N. office. They complained Sri Lanka is being unfairly criticized for alleged abuses as the war was ending in 2009.
They alleged the visit was a step toward subjecting Sri Lanka to an international war crimes investigation.
Three representatives from the U.N. human rights commission have met Sri Lankan government officials and ethnic Tamil politicians and seen areas ravaged by war on their visit.
A U.N. report found evidence the government and Tamil Tiger rebels committed rights violations during the war.
The U.N. Human Rights Council adopted a resolution earlier this year urging Sri Lanka to investigate alleged war crimes committed by both sides. The visits are seen as a follow-up to the resolution, which also asked Sri Lanka to accept expertise from the office of U.N. human rights commissioner.