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The funeral procession for Hamas leader Ismail Haniyeh, who was killed in a strike in Tehran that was blamed on Israel, took place in the Iranian capital on Thursday.
He is expected to be taken to his final resting place in Qatar, where he will be buried in Doha on Friday.
Mr Haniyeh was killed in an attack on a guesthouse in Tehran on Wednesday, which also killed his bodyguard Wasim Abu Shaban. Iran, Jordan, Syria, Hezbollah, Hamas and others have blamed Israel for the killings. Israel has neither confirmed nor denied its involvement.
Iranian Foreign Ministry spokesman Nasser Kanaani called the attack “state and organised terrorism”.
The funeral procession began at Tehran square and ended at Azadi Square, where people threw flowers on Mr Haniyeh's coffin.
Thousands of mourners were seen at the event, which Iranian media described as a “state funeral”, with some people carrying the flags of Palestine, Iran and Hezbollah.
Women were seen dressed in black as they gathered to pay their respects to the late Hamas leader.
High ranking officials from the Iran-backed Axis of Resistance attended.
Iran's Supreme Leader Ali Khamenei recited prayers over the casket of Mr Haniyeh, marking the start of the procession.
"The criminal and terrorist Zionist regime should prepare the ground for a severe punishment for itself with this act, and we consider it our duty to avenge his blood as he was martyred in the territory of the Islamic Republic of Iran," Mr Khamenei said, according to Iran's semi-official news agency, IRNA.
Senior Iranian officials including President Masoud Pezeshkian and the Islamic Revolutionary Guard Corps chief, General Hossein Salami, also attended the ceremony, state TV showed.
Iran issued three days of public mourning following the killing of Mr Haniyeh.
Details are still emerging about the exact circumstances of his killing.
According to the New York Times, which cited seven anonymous Middle Eastern officials, Mr Haniyeh was killed by an explosive device that had been smuggled into the guesthouse where he was staying in Tehran.
The bomb had been hidden in the guesthouse about two months before Mr Haniyeh arrived in Iran, where he was attending the inauguration of Mr Pezeshkian as president.
The guesthouse, which is in the area of Neshat, is protected by the Islamic Revolutionary Guards Corps.
Israel has been widely blamed for carrying out the attack, which it has not denied.
Israel's leaders had vowed to annihilate Hamas, including all its top leadership, following the group's October 7 attacks on Israel.
More than 39,400 Palestinians, most of them civilians, have since lost their lives during Israel's retaliatory war in Gaza.
Iran has threatened revenge for the killing of Mr Haniyeh on its territory.
Mr Khamenei issued an order on Wednesday to strike Israel “directly”, The New York Times reported, citing three unnamed Iranian officials.
The supreme leader gave the order at an “emergency meeting of Iran's Supreme National Security Council” following the attack, it said.
Iran's ambassador to the UN Amir Saeed Iravani also said that his country has the right to “self-defence per international law” in response to the “terrorist and criminal act” which took place on Wednesday.
Mr Iravani added that "the role of the US as a strategic ally and main backer of the Zionist regime should not be ignored."
In a press conference on Wednesday, US State deputy spokesman Vedant Patel refused to answer a question on whether Iran has the right, as a sovereign nation, to defend itself.
The US on Wednesday denied any involvement in the assassination.
“The United States was not aware of or involved in the apparent death of Hamas leader Ismail Haniyeh,” US deputy ambassador to the UN Robert Wood said during an emergency meeting of the Security Council, requested by Iran.
According to the New York Times piece, Israel briefed officials from the US and other Western allies after carrying out the killing.
Meanwhile, protests against the attack were held in the occupied West Bank and various countries around the world, including Lebanon, Turkey, Iraq, Tunisia and Jordan.
In Istanbul, thousands of pro-Palestinian protesters marched through the streets waving Turkish and Palestinian flags.
Protesters were heard chanting "murderer Israel, get out of Palestine" and "thousands of greetings from Istanbul to the resistance in Gaza".
Turkey's President Recep Tayyip Erdogan, who has voiced his support for Hamas, had condemned the "perfidious assassination" of his "brother".
"May God have mercy on my brother Ismail Haniyeh, fallen in martyrdom after this odious attack," Mr Erdogan posted on X, denouncing "Zionist barbarity".
"This shameful act aims to sabotage the Palestinian cause, the glorious Gazan resistance and our Palestinian brothers' just fight, and to intimidate Palestinians," he said.
In Tunisia, protester's gathered in the capital Tunis as part of a demonstration organised by the Popular Current.
In Beirut, thousands had gathered for the funeral of Hezbollah commander Fouad Shukr, who was killed hours before Mr Haniyeh in an Israeli strike on the Lebanese capital.
