Haniyeh’s body is being carried through Tehran towards Azadi Square before being flown to Qatar for burial.
Iran’s Supreme Leader Ayatollah Ali Khamenei has led funeral prayers at a memorial event for Hamas leader Ismail Haniyeh in Tehran.
In the capital’s city centre, thousands of mourners with posters of Haniyeh and Palestinian flags gathered on Thursday at Tehran University.
Following the prayers, massive crowds accompanied the body of Haniyeh and his bodyguard also killed in the strike on Wednesday, in a 5km (3-mile) funeral procession through Tehran towards Azadi (Freedom) Square.
Haniyeh’s body will then be flown to the Qatari capital, Doha, for burial.
The ceremony opened with an address from Iran’s parliament speaker Mohammad Bagher Ghalibaf. “Martyr Ismail Haniyeh was the voice of the Palestinian people all over the world,” he said. “He was not only a leader. He was the wise man.”
Ghalibaf added that Haniyeh’s assassination in Tehran would not go unanswered.
“Our reply will be there. At the right time and the right place. It is difficult for us to have our guest being targeted and assassinated on our soil,” he said.
The mood in Tehran was mixed, said Al Jazeera’s Resul Serdar, commenting from Doha. “On the one hand, Iranians are really irritated by these ongoing killings because this is not the first assassination to have happened in Iran,” he said.
“On the other hand, you will see that the Iranian public is quite concerned about any serious retaliation that could lead to a regional war.”
Haniyeh and his bodyguard were killed in a strike on their accommodation in the Iranian capital early on Wednesday. The Hamas leader was in Tehran for the inauguration of newly elected President Masoud Pezeshkian on Tuesday.
Khamenei promised “harsh punishment” for Israel and said that it was “our duty to seek revenge for his blood as he was martyred in the territory of the Islamic Republic of Iran”.
Pezeshkian said Wednesday that “the Zionists (Israel) will soon see the consequences of their cowardly and terrorist act”.
Hamas political bureau member Musa Abu Marzouk also promised retaliation, saying: “The assassination of leader Ismail Haniyeh is a cowardly act and will not go unanswered.”
Israel has declined to comment on the Tehran strike.
The assassination came just hours after Israel targeted and killed top Hezbollah commander Fuad Shukr in a retaliatory strike on the Lebanese capital, Beirut, sending fears of a wider regional war soaring.
United Nations Secretary-General Antonio Guterres said the strikes in Tehran and Beirut represented a “dangerous escalation”.
All efforts, he said, should be “leading to a ceasefire” in Gaza and the release of captives taken during the Hamas-led October 7 attack on southern Israel.
Gaza’s Ministry of Health says at least 39,445 people have been killed and 91,073 wounded in Israel’s war on Gaza. An estimated 1,139 people were killed in Israel during the Hamas-led attacks and more than 200 were taken captive.
