Deadly Israeli attacks that blew up Hezbollah radios and pagers crossed all red lines, the leader of the heavily armed Iran-backed Lebanese movement said on Thursday, as the United States called for restraint and urgent de-escalation.

Israel has responded to Hezbollah’s fire with strikes in southern Lebanon, and has struck senior figures from the group in the capital Beirut. The exchanges have killed hundreds in Lebanon and dozens in Israel and forced the evacuation of tens of thousands of residents on each side of the border.

Israeli jets bombarded southern Lebanon and staged a show of force over Beirut just as Hezbollah’s leader vowed to avenge the covert operation that turned his fighters into walking booby traps.Hassan Nasrallah admitted that his movement had been dealt “a huge and severe blow” after two days of remote-controlled explosions in electronic devices killed 37 people and wounded thousands more.