TEHRAN, July 31 (Reuters/BBC/AP): Hamas leader Ismail Haniyeh was assassinated in the early hours of the morning in Iran, the Palestinian militant group said on Wednesday, drawing fears of wider escalation in a region shaken by Israel's war in Gaza and a worsening conflict in Lebanon.
Iran's Revolutionary Guards confirmed the death of Haniyeh, hours after he attended a swearing in ceremony for the country's new president, and said it was investigating.
There was no immediate comment from Israel. The Israeli military said it was conducting a situational assessment but had not issued any new security guidelines for civilians.
US Defense Secretary Lloyd Austin said Washington would work to try to ease tensions but said the United States would help defend Israel if it were attacked.
The news, which came less than 24 hours after Israel claimed to have killed the Hezbollah commander it said was behind a deadly strike in the Israeli-occupied Golan Heights, appears to set back chances of any imminent ceasefire agreement in Gaza.
"This assassination by the Israeli occupation of Brother Haniyeh is a grave escalation that aims to break the will of Hamas," senior Hamas official Sami Abu Zuhri told Reuters.
He said Hamas, the Palestinian Islamist group that ruled Gaza, would continue the path it was following, adding: "We are confident of victory."
Iran vows to avenge the killing of Hamas's political leader Ismail Haniyeh, who died in an overnight air strike in Tehran, according to Iranian media.
Hamas and Iran blame Israel for the strike - Israel hasn't commented but has previously vowed to eliminate the group's leaders.
Iran - Hamas's most important backer - declares three days of mourning and promises "harsh punishment" against Israel.
Palestinian President Mahmoud Abbas condemned the killing of Haniyeh and Palestinian factions in the occupied West Bank called for a general strike and mass demonstrations.
Haniyeh, normally based in Qatar, has been the face of the Palestinian group's international diplomacy as the war set off by the Hamas-led attack on Israel on Oct 7 has raged in Gaza, where three of his sons were killed in an Israeli airstrike.
The International Criminal Court prosecutor office requested an arrest warrant for him over alleged war crimes at the same time it issued a similar request against Israeli Prime Minister Benjamin Netanyahu.
UN report says Palestinian
detainees face torture
The U.N. human rights office issued a report Wednesday saying Palestinian detainees taken by Israeli authorities since the Oct. 7 attacks in Gaza have faced waterboarding, sleep deprivation, electric shocks and other torture and mistreatment.
The report on detention says Israel's prison service held more than 9,400 "security detainees" as of the end of June, and some have been held in secret without access to lawyers or respect for their legal rights.
A summary of the report, based on interviews with former detainees and other sources, decries a "staggering" number of detainees - including men, women, children, journalists and human rights defenders - and said such practices raise concerns about arbitrary detention.
"The testimonies gathered by my office and other entities indicate a range of appalling acts, such as waterboarding and the release of dogs on detainees, amongst other acts, in flagrant violation of international human rights law and international humanitarian law," said U.N. Human Rights Chief Volker Türk in a statement.