Watch a view of a blast site in southern Beirut on Tuesday 2 January after Hamas confirmed its deputy leader, Saleh al Arouri, had been killed by an explosion.
Lebanon’s state-run National News Agency said the blast killed four people and was carried out by an Israeli drone. Israeli officials declined to comment.
If Israel is behind the attack it could mark a major escalation in the Middle East conflict. Hezbollah leader Sayyed Hassan Nasrallah has vowed to retaliate against any Israeli targeting of Palestinian officials in Lebanon.
Hamas official Bassem Naim confirmed to The Associated Press that Arouri was killed in the blast. A Hezbollah official speaking on condition of anonymity in line with regulations also said Arouri was killed.
Arouri, one of the founders of Hamas' military wing, had headed the group's presence in the West Bank. Israel's prime minister Benjamin Netanyahu had threatened to kill him even before the Hamas-Israel war began on 7 October.