The Israeli military launched airstrikes in Lebanon hours after it struck the Gaza Strip early Friday.
In a statement, it said it struck targets belonging to the Palestinian resistance group Hamas in southern Lebanon.
The Israeli army said it would not allow Hamas "to operate from within Lebanon" and "holds the state of Lebanon responsible for every directed fire emanating from its territory."
In the early hours of Friday, the Israeli military struck two tunnels in Beit Hanoun and Khan Yunis and two weapons factories in Gaza in response to "Hamas' security violations."
Reacting to the Israeli airstrikes in Gaza, Hazem Kassem, a spokesman for Hamas, said Israel "bears full responsibility" for the escalation and the aggression against Jerusalem and Gaza.
The group launched rockets from the Gaza Strip at Israel after the latest strikes.
The official Israeli channel KAN reported Friday morning that 40 rockets were launched overnight from the Gaza Strip toward adjacent Israeli settlements.
About half of the missiles were intercepted by the Iron Dome system, while the rest fell in open areas, according to the same source.
The Israeli army also issued a warning on Twitter saying sirens are sounding in southern Israel.
Sirens were also triggered in the city of Ashkelon, as well as the Gaza periphery settlements after rockets were fired from the Gaza Strip.
The developments came after Israeli forces stormed the Al-Qibli Prayer Hall in the Al-Aqsa Mosque complex in occupied East Jerusalem and forcibly removed Palestinian worshippers for two nights in a row.