GENEVA — A United Nations report published Tuesday says the Yemeni government has used excessive and deadly force against peaceful demonstrators, killing hundreds and wounding thousands since the beginning of the year.

The report, published by the Office of the High Commissioner for Human Rights, urged immediate international action to alleviate a humanitarian crisis and prevent the country from falling into further chaos.

A delegation sent by the office visited Yemen’s three main cities at the end of June, according to the report, and found “an overall situation where many Yemenis peacefully calling for greater freedoms, an end to corruption and respect for rule of law were met with excessive and disproportionate use of lethal force by the state.”

The United Nations team said it met with officials including the vice president and acting head of state, Abed Rabbo Mansour al-Hadi, as well as political party leaders, members of parliament and the judiciary, lawyers and other prominent private citizens. Over nine days in Sana, Aden and Taiz, the team collected thousands of pages of documents and photographs, 1,800 videos and 160 compact discs — evidence that it “archived for appropriate future use, ” the report said.