Massive consecutive strikes hit Beirut's southern suburbs early on Sunday, Reuters eyewitnesses said, sending booms across the Lebanese capital and sparking flashes of red and white for nearly 30 minutes visible from several kilometres away.
Israel said its air force had "conducted a series of targeted strikes on a number of weapons storage facilities and terrorist infrastructure sites belonging to the Hezbollah terrorist organization in the area of Beirut".
The Israeli military said that before the strike, it took steps "to mitigate the risk of harming civilians, including advancing warnings to the population in the area".
Israel has been expanding its actions in Lebanon.
On Saturday, it made its first strike in the northern city of Tripoli, a Lebanese security official said, and Israeli troops launched raids in the south.
Israeli military spokesperson Rear Admiral Daniel Hagari said on Saturday that Israel had killed 440 Hezbollah fighters in its ground operations in southern Lebanon and destroyed 2,000 Hezbollah targets. Hezbollah has not released death tolls.
Israel says it stepped up its assault on Hezbollah to enable the safe return of tens of thousands of citizens to homes in northern Israel, bombarded by the group since last Oct. 8.
By Maya Gebeily and Laila Bassam