Iranian leaders vowed revenge on Thursday for two explosions that killed nearly 100 people at a ceremony to commemorate top Revolutionary Guards commander Qassem Soleimani on the anniversary of his death in a U.S. drone attack.

"A very strong retaliation will be handed to them on the hands of the soldiers of Soleimani," First Vice President Mohammad Mokhber told reporters at a hospital were some of the wounded from Wednesday's blasts were receiving treatment.

Tehran has blamed the explosions on unspecified "terrorists", but no one has yet claimed responsibility for the bloodiest such attacks since the 1979 Islamic Revolution.

An unnamed source told the state news agency IRNA that the first explosion at the cemetery in the southeastern city of Kerman "was the result of a suicide bomber's action".

"The cause of the second blast was most likely the same," the source told IRNA.

State TV showed crowds gathered at dozen cities across Iran, including Soleimani's home town 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 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 the "heinous and inhumane crime", and Iran's top authority, Supreme Leader Ayatollah Khamenei, vowed revenge for the twin bombings, that also wounded 284 people, including women and children.

EARLIER ATTACKS

The United States on Wednesday said it was not involved in any way in the explosions and had no reason to believe Israel was.

Washington said the blasts appeared to represent "a terrorist attack" of the type carried out in the past by Islamic State militants.

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.

In 2022, the Sunni Muslim militant group Islamic State claimed responsibility for a deadly attack on a Shi'ite shrine in Iran which killed 15 people.

Earlier attacks claimed by Islamic State include twin bombings in 2017 which targeted Iran's parliament and the tomb of the Islamic Republic's founder, Ayatollah Ruhollah Khomeini.

The U.S. assassination of Soleimani in a Jan. 3, 2020, drone attack at Baghdad airport, and Tehran's retaliation - by attacking two Iraqi military bases that house U.S. 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 U.S. 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 in retaliation for their Oct. 7 rampage through southern Israel.

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.

U.S. 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.