Ismail Haniyeh, the leader of the Palestinian militant group Hamas, was been killed in an attack in Tehran early July 31 morning, according to Iranian state media.

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 of Iranian territory, Israel's Haaretz reported citing Lebanese news reports. 

Fars News Agency, which is closely aligned with the IRGC, reported that the attack occurred at a special residence for disabled veterans where Haniyeh was staying. He was in Iran to attend the presidential inauguration ceremony. "Further investigations are underway and exact details will be announced soon," the Fars report added.

Now confirmed, the killing of Hamas' top political leader on Iranian soil would mark a significant escalation in regional tensions and could have far-reaching consequences for the Israeli-Palestinian conflict and Iran's role in the region.

Iran's Supreme National Security Council's spokesman has said the assassination of Hamas leader Ismail Haniyeh is a despicable act, and that it's perpetrators will get a response, according to Lebanese network Al Mayadeen.

Mousa Abu Marzouk, a member of the Hamas political bureau said the assassination of leader Ismail Haniyeh was a "cowardly act" that will not go unanswered.

Sami Abu Zuhri, another Hamas leader, also said: “We are in an open war for the liberation of Jerusalem and are ready to pay various costs.”

President of the Palestinian National Authority Mahmoud Abbas condemned the killing of Haniyeh as a "cowardly act" and a serious escalation.

He urged the Palestinian people and their forces to "unite, remain patient, and stand firm against the Israeli occupation", his office said in a statement.

The leader of the Iraqi National Wisdom Movement, Ammar al-Hakim in a message of condolence, declared that the actions of the "Zionist regime will not prevent the Palestinian nation from advancing on the path to victory."

Meanwhile, Houthi movement of Yemen, also known as Ansarullah, said the assassination of "brother Ismail Haniyeh" is a terrorist crime and a clear violation of laws.

Israeli officials have not reacted to the development. According to CNN, the Israeli military said it doesn't respond to reports in foreign media.

A spokesperson for the White House said it has seen the reports, but declined to immediately comment further.

Meanwhile, there have been popular calls for a general strike across Palestine following the assassination.

The attack comes after a strike at a football pitch in the Golan Heights, which killed 12 children and teenagers in recent days. Israel blamed Hezbollah for the attack and vowed retaliation, although the Iran-backed group denied responsibility. 

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.

Later, it announced that it had eliminated Fouad Shokr, an influential advisor to Hezbollah Leader Hassan Nasrallah, but Hezbollah said he had survived the strike.