TEHRAN — Hamas political chief Ismail Haniyeh was killed with a "short-range projectile" fired from outside his guesthouse in Tehran, according to Iran's Revolutionary Guard Corps (IRGC).

The paramilitary organization said the projectile weighed about 7kg (16lbs) and caused a "strong blast," killing Haniyeh and his bodyguard last Wednesday. Haniyeh had been visiting the Iranian capital for the inauguration of President Massoud Pezeshkian.

The IRGC accused Israel, with US support, of designing and implementing the operation. Israel has not commented on Haniyeh's death.

Western media reports suggest that explosives were planted in the guesthouse by Israeli operatives, conflicting with the IRGC's account. The incident has embarrassed Iran and the IRGC, especially given the intense security on the day of the attack.

Dozens of IRGC officers have been arrested or dismissed since Haniyeh's death, according to the New York Times. The IRGC's intelligence agency has taken over the investigation, interrogating staff members at Haniyeh's guesthouse and seizing their electronics.

In response to the security breach, the security details of Iranian politicians have been overhauled. Supreme Leader Ayatollah Ali Khamenei led prayers for Haniyeh but was quickly escorted away by his security detail afterward.

The IRGC's statement followed a report by Britain's Daily Telegraph that Haniyeh was killed by bombs planted in his room by agents of Israel's Mossad intelligence agency.

The New York Times also reported that Haniyeh was killed by explosives, potentially planted up to two months earlier. Hamas officials noted that Haniyeh had stayed at the guesthouse before and had made numerous visits to Iran since becoming the head of the political bureau in 2017.

If true, these reports would indicate a significant failure for the IRGC, highlighting Mossad's ability to operate within Iran. Both Iran and Hamas have vowed to retaliate for Haniyeh's death. The IRGC promised "severe punishment" for Israel at an appropriate time, while Hezbollah has also vowed reprisals after one of their commanders was killed in an Israeli strike.

The situation has escalated regional tensions, with Prime Minister Benjamin Netanyahu warning Israelis of challenging days ahead and preparing for any scenario. The US has deployed additional warships and fighter jets to the Middle East to help defend Israel from potential attacks by Iran. UK Foreign Secretary David Lammy warned of a rapidly deteriorating situation on the ground.

Israeli officials, including the heads of Mossad and Shin Bet, are in Cairo for ceasefire talks with Egyptian intelligence chief Abbas Kamel. However, US President Joe Biden acknowledged that Haniyeh's death had damaged the ceasefire negotiations. The conflict, which began in October, has resulted in significant casualties. — Agencies