The United Nations on Tuesday urged all parties to "come to their senses" and end the war in the Middle East, with fear and panic spreading across the region and beyond.
UN human rights chief Volker Turk said he was "deeply shocked" by how the conflict was affecting civilians.
"The fear, the panic, the anxiety experienced by millions of people in the Middle East and beyond is palpable -- and was entirely avoidable," his spokeswoman Ravina Shamdasani told a press conference in Geneva.
"The situation is worsening and widening by the hour, playing out our worst fears."
Turk "is deeply shocked by the impacts of the widespread hostilities on civilians and civilian infrastructure since the conflict erupted on Saturday with Israel and the United States of America's attacks on Iran, Iran's response against states across the region, as well as Hezbollah's subsequent entry into the conflict," she said.
Turk called on all parties to exercise maximum restraint, prevent further escalation, and take all feasible measures to protect civilians and critical infrastructure.
"Returning to the negotiating table is the one and only way to bring an end to the killing, destruction and despair," Shamdasani said.
Turk "implores all parties to come to their senses, and to end this violence", she added.
Shamdasani said the laws of war were clear: civilians and civilian objects are protected, and all states and armed groups must abide by the law.
- Girls' school attack -
Iran has claimed that 168 people were killed in a strike on a girls' school in the southern town of Minab.
Turk is calling for a prompt, impartial and thorough investigation into the attack.
"The onus is on the forces that carried out the attack to investigate it. We call on them to make public the findings and ensure accountability and redress for victims," Shamdasani said.
The UN rights office voiced grave concern for the welfare of Iranian citizens, "given the government's record of cracking down with lethal force on broad scale against those who oppose their rule".
It called for the immediate restoration of telecoms services, saying many Iranians were again unable to get online and access essential information as hostilities continue.
"We are also concerned for the welfare of hundreds of political prisoners that continue to be arbitrarily held in Iran. Every effort must be taken to ensure their protection, and we urge their prompt release."
