Israel's air force has carried out three strikes in the Gaza Strip, witnesses have said.
Two airstrikes hit the southern town of Khan Yunis, early on Sunday. The third was near the southern town of Rafah, near the Egyptian border, Palestinian witnesses said.
There were conflicting reports concerning the targets and no reported casualties.
An Israeli army spokesperson confirmed the air force had carried out strikes in the Gaza Strip but told the AFP news agency she could not give further details.
The Israeli authorities also closed on Sunday until further notice the Kerem Shalom goods crossing following a rocket attack, the defence ministry said.
Prime Minister Benjamin Netanyahu told Sunday's weekly cabinet meeting that Israel would retaliate with great force against any rocket or missile fire.
"I want to make it clear that we will respond in a very offensive way against any rockets or missiles. We will take all necessary measures to ensure the security of Israelis... on all fronts," his office quoted him as saying.
Israel had not carried out Gaza airstrikes since early April, when it launched the first strikes since an Egyptian-brokered truce in November ended a deadly eight-day conflict between Tel Aviv and fighters belonging to Hamas, which governs the territory.
On April 19, two rockets fired from the Gaza Strip hit southern Israel without causing any casualties or damage.