Iran's Foreign Ministry spokesman Nasser Kanaani has strongly condemned the assassination of Hamas political bureau chief Ismail Haniyeh in Tehran, vowing that his death would not be in vain.

The Islamic Revolutionary Guard Corps (IRGC) said in a statement that Haniyeh and one of his bodyguards died when their residence in northern Tehran was struck by an aerial projectile at approximately 2 a.m. local time. Unconfirmed reports suggest the projectile was launched from outside Iranian territory, Israel's Haaretz reported. The attack is a massive blow to the Iranian security establishment, with officials in the capital reportedly in shock over the incident. 

"The pure blood of martyr Ismail Haniyeh, who spent his life in honourable struggle against the usurping Zionist entity and on the path to liberate holy Jerusalem, will never be wasted," Kanaani said in a statement.

Kanaani said that relevant Iranian institutions are investigating the details of the incident.

"The martyrdom of brother Ismail Haniyeh in Tehran will strengthen the deep and solid ties between the Islamic Republic of Iran and dear Palestine and the resistance," he added.

Haniyeh had arrived in Tehran to participate in the inauguration ceremony of Iran's new President Masoud Pezeshkian, whom he had met on July 30 evening.

The IRGC statement said the cause and dimensions of this incident would be announced later.

No images or videos of the assassination site have been released or leaked yet, but the location is believed to be in northern Tehran, IRGC-linked Tasnim reported.

Former IRGC commander Mohsen Rezaee said: "This martyrdom is another testament to the cowardice of the criminal Tel Aviv gang, from the killing of Palestinian women, children and the elderly to trampling on human rights and violating the legal boundaries and international laws of countries by assassinating beloved leaders of nations."

He added, "How foolish are those who think that such cowardly displays of power can compensate for their weakness and helplessness in facing the heroic and invincible children of Palestine? Israel will pay a heavy price."

This assassination comes amid rising tensions in the region, with reports of an Israeli airstrike on southern Beirut on Tuesday night that reportedly killed three people and injured 86 others.

Israeli officials have not commented on the incident. The assassination, if confirmed to be an Israeli operation, could potentially escalate regional conflicts and have a huge impact on ongoing diplomatic efforts.

Earlier, on July 30, Israel conducted airstrikes targeting Hezbollah positions in southern Lebanon. The Israeli Defence Forces (IDF) said at the time that the attack targeted a Hezbollah commander responsible for the strike at Golan.