Iran has arrested more than two dozen individuals, including senior intelligence officers, military officials, and staff at a military-run guesthouse in Tehran, following a major security breach that allowed for the assassination of a top Hamas leader, according to two Iranians familiar with the investigation.

The arrests followed the killing of Ismail Haniyeh in an explosion early Wednesday. Haniyeh, who had led Hamas’s political office in Qatar, was visiting Tehran for the inauguration of Iran’s new president and was staying at the guesthouse in northern Tehran. This event highlighted a significant security lapse, as the assassination occurred in a heavily guarded compound in the capital shortly after the new president's swearing-in ceremony.

Ali Vaez, the Iran director for the International Crisis Group, stated that the assassination undermines the perception of Iran's ability to protect its homeland and key allies, potentially signalling to adversaries that the regime is vulnerable.

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Officials have suggested that the bomb responsible for Haniyeh's death was planted in his room up to two months before his arrival. Both Iranian and Hamas officials, as well as several U.S. officials, have accused Israel of the assassination. Israel, which aims to dismantle Hamas's capabilities, has not claimed responsibility.

The Revolutionary Guards Corps’ specialized intelligence unit has taken over the investigation, aiming to identify the members of the assassination team. The Guards have not disclosed any details of the arrests or the investigation but have promised severe retaliation, as echoed by Iran’s supreme leader, Ayatollah Ali Khamenei.

The intensity of the investigation reflects the assassination's significant impact on Iran's leadership. The blast, which also killed Haniyeh’s Palestinian bodyguard, was not just a security failure but a blow to Iran's reputation and an indication of potential Mossad infiltration.

The security breach has led to heightened concerns, particularly given Haniyeh's recent meeting with Khamenei. During Haniyeh’s funeral, Khamenei was surrounded by an unusually tight security detail.

Also Read: Ismail Haniyeh martyred by explosive device in Tehran guesthouse: NYT report

The covert conflict between Iran and Israel has been ongoing for years, with Israel assassinating numerous Iranian scientists and commanders and conducting various sabotage operations. Iran has consistently vowed to find and punish the culprits, though with limited success.

Following Haniyeh’s assassination, Iranian security agents conducted a thorough search of the guesthouse, quarantined staff, and confiscated electronic devices. They also arrested senior military and intelligence officials involved in capital security. The investigation includes scrutinizing surveillance footage and flight lists from Tehran’s airports, with suspicions that Mossad operatives are still in the country.

A member of the Revolutionary Guards, speaking anonymously, indicated that security protocols have been overhauled, including changes to senior officials' security details and electronic equipment. Former President Hassan Rouhani stated that Israel's assassination of Haniyeh was an attempt to destabilize Iran at the start of a new government, emphasizing the need for cooperation among all security branches to counter the threat.