BEIRUT: Hezbollah's leader Sheikh Hassan Nasrallah was killed by an Israeli airstrike on Beirut, leaving a vacuum inside a movement that suffered losses among its ranks due to months of Israeli assassinations.

Nasrallah became Hezbollah's secretary-general in 1992 at the age of 35 after which he led the movement for the majority of its existence.

There are two leading figures who are being considered to Nasrallah’s successor — Hashem Safieddine and Naim Qassem. Here's what you need to know about them. 

Hashem Safieddine

Hashem Safieddine, a potential successor to his slain cousin Nasrallah, is one of Hezbollah's most prominent figures and has deep religious and family ties to the movement's patron Iran.

Safieddine bears a striking resemblance to his charismatic maternal cousin Nasrallah but is several years his junior, aged in his late 50s or early 60s.

A source close to Hezbollah, requesting anonymity as they were not authorised to speak to the media, said the grey-bearded, bespectacled Safieddine was the "most likely" candidate for party’s top job.

The United States and Saudi Arabia put Safieddine, who is a member of Hezbollah's powerful decision-making Shura Council, on their respective lists of designated "terrorists" in 2017.

The US Treasury described him as "a senior leader" in Hezbollah and "a key member" of its executive.

While Hezbollah deputy chief Naim Qassem automatically takes over the Hezbollah leadership after Nasrallah’s death, the Shura Council must meet to elect a new secretary-general.

Safieddine has strong ties with Iran after undertaking religious studies in Qom.

His son is married to the daughter of General Qasem Soleimani, the commander of Iran’s Revolutionary Guards’ foreign operations arm who was killed in a 2020 US strike in Iraq.

Safieddine has the title of Sayyed, his black turban marking him, like Nasrallah, as a descendant of the Prophet Mohammed.

Unlike Nasrallah, who lived in hiding for years, Safieddine has appeared openly at recent political and religious events.

Naim Qassem

Qassem, Hezbollah’s deputy secretary-general, is also at the pole position, who has been noted as the group’s "number two".

The 71-year-old was among the founding members of the fighter group in the early 1980s. He’s regarded as Hezbollah’s one of the foundational religious scholars, who has taught religious students at Beirut for decades.

Qassem used to look after the fighters' educational matters and also oversaw their parliamentary activities.

The Iran-backed group’s co-founder and then-secretary general Abbas al-Musawi elected him deputy secretary-general in 1991.