At least 50 people were killed in a stampede as mourners packed streets for the funeral of a slain Iranian military commander in his hometown on Tuesday, forcing his burial to be postponed, state media reported.
Tens of thousands of people had gathered in the southeastern city of Kerman to pay tribute to General Qassem Soleimani, whose killing in a U.S. drone strike in Iraq on Friday plunged the region into a new crisis and raised fears of a broader conflict.
A senior Iranian official said Tehran was considering several scenarios to avenge his killing. Other senior figures have said Iran will match the scale of Soleimani's killing when it responds but that it will choose the time and place.
Tuesday's stampede broke out amid the crush of mourners, killing 50 people, Iran's ISNA news agency said, quoting the chief coroner for Kerman province, Abbas Amian. About 213 people were injured, an emergency services official told the semi-official Fars news agency.
The burial of Soleimani had been postponed, ISNA said, without adding long any delay would last.
"Today because of the heavy congestion of the crowd unfortunately a number of our fellow citizens who were mourning were injured and a number were killed," emergency medical services chief Pirhossein Kolivand told state television.
The body of Soleimani, a national hero to many Iranians but viewed as a dangerous villain by Western governments opposed to the Islamic Republic, had been taken to Iraqi and Iranian cities before arriving in Kerman for burial.
In each place, huge numbers of people filled thoroughfares, chanting "Death to America" and weeping with emotion. Supreme Leader Ali Khamenei shed tears when leading prayers in Tehran.
Soleimani, who commanded the elite Quds Force, was responsible for building up Tehran's network of proxy armies across the Middle East. He was a key figure in orchestrating Iran's long-standing campaign to drive U.S. forces out of Iraq.
Iran's opponents say its proxies have fuelled conflicts, killing and displacing people in Iraq, Syria and beyond. Tehran says any operations abroad are at the request of governments and that it offers "advisory support".
The U.S. defense secretary denied reports the U.S. military was preparing to withdraw from Iraq, where Tehran has vied with Washington for influence since the 2003 U.S. invasion.
"We will take revenge, a hard and definitive revenge," the head of Iran's Revolutionary Guards, General Hossein Salami, told the crowds in Kerman before the stampede.
Ali Shamkhani, secretary of the Supreme National Security Council, said 13 "revenge scenarios" were being considered, Fars news agency reported. Even the weakest option would prove "a historic nightmare for the Americans," he said.
Iran, whose coastline runs along a Gulf oil shipping route that includes the narrow Strait of Hormuz, has allied forces across the Middle East through which it can act. Representatives from those groups, including the Palestinian group Hamas and Lebanon's Hezbollah movement, attended funeral events in Tehran.
Despite its strident rhetoric, analysts say Iran will want to avoid any conventional conflict with the United States and is likely to focus on asymmetric strikes, such as sabotage or other military action via proxies.
Trump has promised to target 52 Iranian sites if Iran retaliates.
Reuters and other media reported on Monday that the U.S. military had sent a letter to Iraqi officials informing them U.S. troops were preparing to leave. But U.S. Defense Secretary Mark Esper denied there had been any decision to pull out.
About 5,000 U.S. troops are still in Iraq, where there has been a U.S. military presence since Saddam Hussein was toppled in 2003.
Iraq's parliament, dominated by lawmakers representing Muslim Shi'ite groups who have been united by the killing of Soleimani alongside an Iraqi militia leader, passed a resolution on Sunday calling for all foreign troops to leave.
Iraq's caretaker Prime Minister Abdel Abdul Mahdi told the U.S. ambassador to Baghdad the resolution must be implemented.
Friction between Iran and the United States has risen since Washington withdrew in 2018 from a nuclear deal between Tehran and world powers.
The United States has imposed new economic sanctions on Iran, slashing Iranian oil exports, and Tehran said on Sunday it was dropping limitations on uranium enrichment, in its latest step back from commitments to the deal.
Washington denied a visa to Iranian Foreign Minister Mohammad Javad Zarif to allow him to attend a U.N. Security Council meeting in New York on Thursday, a U.S. official said.
Trump's U.S. political rivals have challenged his decision to order the killing of Soleimani and questioned its timing in a U.S. election year. His administration said Soleimani was planning new attacks on U.S. interests without giving evidence.
U.S. general Milley said the threat from Soleimani was imminent. "We would have been culpably negligent to the American people had we not made the decision we made," he said.
Trump administration officials will provide a classified briefing for U.S. senators on Wednesday on events in Iraq after some lawmakers accused the White House of risking a broad conflict without a strategy.