Fears of a regional war in the Middle East are growing after a top Hamas official was assassinated in a suburb of Beirut, Lebanon, on Tuesday. Hamas’s deputy leader, Saleh al-Arouri, was killed in a suspected Israeli drone strike that also killed six other members of Hamas. Al-Arouri was the chief of Hamas’s operations in the occupied West Bank. He was also credited with strengthening ties between Hamas and the Lebanese group Hezbollah. In the West Bank, Palestinians are holding a general strike today to protest al-Arouri’s assassination.

Hezbollah’s leader, Hassan Nasrallah, is scheduled to give a speech today responding to the killing. While Israel has not claimed responsibility for the assassination, one prominent Israeli lawmaker congratulated the Mossad and Shin Bet on social media. An Israeli army spokesperson said the military was in a “very high state of readiness in all arenas, in defense and offense.” Lebanon’s Prime Minister Najib Mikati condemned the drone strike, warning that the attack “aims to draw Lebanon into a new phase of confrontations.” U.N. officials in Lebanon are urging all sides to show restraint to avoid a wider conflict.