The escalation comes after U.S. envoy Amos Hochstein traveled to the region in pursuit of a deal to end months of fighting between Israel and Hezbollah that has erupted into full-on war.

A powerful Israeli air strike flattened a residential building in central Beirut early Saturday, killing at least 11 people and wounding 63 others, according to witnesses and the Health Ministry's initial count.

The strikes, which destroyed an eight-story building and left a crater in the ground, were the fourth in Beirut in less than a week.