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Daesh claimed responsibility on Thursday for two explosions in Iran that killed nearly 100 people and wounded scores at a memorial for top commander Qassem Soleimani who was killed in Iraq in 2020 by a US drone.
In a statement posted on its affiliate Telegram channels, the militant group said two Daesh members had detonated their explosive belts in the crowd which had gathered at the cemetery in the southeastern Iranian city of Kerman on Wednesday for the anniversary of Soleimani's death.
Tehran earlier blamed the explosions on "terrorists" and vowed revenge for the bloodiest such attacks since the 1979 Islamic Revolution. The twin blasts also wounded 284 people, including women and children.
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"A very strong retaliation will be meted out to them by the hands of the soldiers of Soleimani," Iran's First Vice-President Mohammad Mokhber told reporters in Kerman.
Earlier, an unnamed source told the state news agency IRNA that the first explosion at the cemetery in Kerman, Soleimani's home town, "was the result of a suicide bomber's action".
"The cause of the second blast was most likely the same," the source told IRNA.
The United Nations Security Council in a statement condemned Wednesday's "cowardly terrorist attack" in Kerman and sent its condolences to the victims' families and the Iranian government.
State TV showed crowds gathered at dozen cities across Iran, including Kerman, chanting: "Death to Israel" and "Death to America".
Iranian authorities have called for mass protests on Friday, when the funerals of the victims of the twin blasts will be held, state media reported.
Iran's powerful Revolutionary Guards Corps described the attacks as a cowardly act "aimed at creating insecurity and seeking revenge against the nation's deep love and devotion to the Islamic Republic".
The Guards commander in Kerman denied state media reports of a shooting in Kerman on Thursday.
Iranian President Ebrahim Raisi has condemned Wednesday's "heinous and inhumane crime". Iran's top authority, Supreme Leader Ayatollah Khamenei, vowed revenge for the bombings.
The United States denied on Wednesday any involvement in the explosions and said it also had no reason to believe Israel was involved. It said the blasts appeared to represent "a terrorist attack" of the type carried out in the past by Daesh.
Tehran often accuses its arch enemies, Israel and the United States, of backing anti-Iran militant groups that have carried out attacks against the Islamic Republic in the past. Baluchi militants and ethnic Arab separatists have also staged attacks in Iran.
The US assassination of Soleimani in a January 3, 2020, drone attack at Baghdad airport, and Tehran's retaliation — by attacking two Iraqi military bases that house US troops — brought the United States and Iran close to full-blown conflict.
As chief commander of the elite Quds force, the overseas arm of Iran's Revolutionary Guard Corps (IRGC), Soleimani ran clandestine operations abroad and was a key figure in Iran's longstanding campaign to drive US forces from the Middle East.
Tensions between Iran and Israel, along with its ally the United States, have reached a new high over Israel's war on Iran-backed Hamas militants in Gaza.
Yemen's Iran-backed Houthi militia have attacked ships they say have links to Israel in the entrance to the Red Sea, one of the world's busiest shipping lanes.
US forces have come under attack from Iran-backed militants in Iraq and Syria over Washington's backing of Israel and have carried out their own retaliatory air strikes.
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