The assassination plot for Hamas political leader Haniyeh Ismail took more than two months to execute, according to a new incredible report.
Haniyeh was targeted by an explosive device hidden in a heavily guarded complex in Tehran where he was staying.
But Middle Eastern sources have told the New York Times that the device was smuggled into his guesthouse more than two months ago.
The guesthouse is run and protected by the Islamic Revolutionary Guards Corps and is part of a large compound, known as Neshat, in an upscale neighborhood of northern Tehran.
The bomb was detonated remotely once it was confirmed that he was inside his room at the guesthouse. The blast also killed a bodyguard.
The explosion shook the building, shattered some windows and caused the partial collapse of an exterior wall, according to sources.
Mr Haniyeh, who had led Hamas’s political office in Qatar, had stayed at the guesthouse several times when visiting Tehran.
He was there this week in Iran’s capital for the presidential inauguration.
Hamas and Iran blame Israel for the strike and have vowed to avenge his death.
Israel hasn’t commented but has previously promised to eliminate the group’s leaders.
Benjamin Netanyahu made no mention of Haniyeh’s killing in a televised statement on Wednesday evening but said Israel had delivered crushing blows to Iran’s proxies of late, including Hamas and Hezbollah, and would respond forcefully to any attack.
He said: “We are prepared for any scenario and we will stand united and determined against any threat.
“Israel will exact a heavy price for any aggression against us from any arena.”
Haniyeh, 62, is the most senior leader to be killed since the October 7 attacks. A funeral was held in Tehran today.
The killing came just hours after an Israeli strike on the Lebanese capital Beirut and has heightened fears of wider conflict in the Middle East.
The latest events appear to set back chances of any imminent ceasefire agreement in the nearly 10-month-old war in Gaza between Israel and the Iran-backed Hamas.