Israel's foes vowed revenge after Hezbollah leader Hassan Nasrallah was killed in an Israeli air strike on a suburb of Beirut. Several world powers warned of the killing's potential repercussions as the spectre of all-out war looms over the Middle East. United Nations chief Antonio Guterres expressed grave concern over the escalation of events in Beirut. Palestinian militant group Hamas condemned the killing as a cowardly terrorist act, while Palestinian president Mahmud Abbas offered condolences to Lebanon. Iran's foreign ministry said Nasrallah's work would continue after his death, and Russia's foreign ministry condemned the political murder and urged Israel to cease military action in Lebanon.