Hezbollah has pounded northern Israel with 140 rockets, a day after the militant group’s leader vowed to retaliate against Israel for a mass bombing attack, the Israeli military and the militant group said.

The strike in Beirut extended a string of Israeli attacks that have injured thousands and left U.S. and regional officials worried about a wider conflict.

Israel is attempting a risky strategy, increasing the intensity of its attacks in an attempt to force Hezbollah to back down, while raising the chances of an aggressive response that devolves into a land war.