Hungarian police fired tear gas and water cannon at protesting migrants demanding to be allowed to enter from Serbia as a border crackdown by Budapest turned violent.
"I was shocked to see how these refugees and migrants were treated, it's not acceptable," Ban told a news conference on Wednesday.
"All the countries have their domestic problems, but since they are the people fleeing the wars and persecutions, then we must show our compassionate leadership," he said, Reuters reported.
"First and foremost we have to provide life-saving assistance and shelter and ... sanitation, then we can discuss how they should be treated, accommodated," Ban said.
The biggest flow of immigrants into Western Europe since World War Two has sown discord across the continent, fuelling the rise of far-right political parties and jeopardizing the 20-year-old Schengen border-free travel zone.
"They must be treated with human dignity and human rights," Ban added. "That's my consistent message to European and Asian leaders."
Hungary on Wednesday detained 29 people as migrants demanding to be let through the country's newly shut EU frontier clashed with riot police firing water cannon and tear gas while refugees searched for new ways to enter the bloc.
Hungary's decision this week to shut the EU's external border with Serbia was the most forceful attempt yet by a European country to reduce the flood of refugees and economic migrants overwhelming the bloc.