Many people around the world are marking World Refugee Day Wednesday by paying tribute to the more than 42 million people who have been forcibly displaced from their homes.

In a special message, U.N. Secretary-General Ban Ki-moon said “refugees leave because they have no choice.” He said everyone must choose to help.

U.S. Secretary of State Hillary Clinton said Wednesday the United States joins the international community in commemorating the courage and determination of the millions of refugees. She said the U.S. is committed to protecting and assisting displaced people.

On Tuesday, the U.N. High Commissioner for Refugees, Antonio Guterres visited Ecuador, where he pledged to continue working to ensure the rights of the largest refugee population in South America. He is spending World Refugee Day in Rio de Janeiro at a U.N. environmental summit.

In its annual report this week, the U.N. refugee agency said a record 800,000 people were forced to flee across borders last year, more than at any time since 2000. The agency said those refugees were among the 4.3 million people who were displaced last year, largely because of humanitarian crises in Ivory Coast, Libya, Somalia, Sudan, and other countries.

Mr. Ban said those numbers are more than statistics. He said they are people and families whose lives have been upended, whose communities have been destroyed and whose future is uncertain.

The U.N. refugee agency says one out of every four refugees in the world is from Afghanistan, and 95 percent of them live in Iran or Pakistan.

Since 2002, about 5.5 million Afghans have returned to their country. But 1.7 million are still registered in Pakistan, scattered among 80 camps.

While millions of Afghans have gone home, the agency says many often find it hard to reintegrate into the villages they left. Some have returned to Pakistan.