Israel launched air strikes in the Gaza Strip on Monday after a rocket attack near Tel Aviv wounded seven people, prompting Prime Minister Benjamin Netanyahu to cut short a visit to the United States.
Netanyahu had threatened strong retaliation for the long-range rocket salvo amid accusations from opponents in a closely contested election, two weeks away, that he has been showing weakness in the face of security challenges from Gaza militants.
"The Israel Defence Forces have begun striking Hamas terror targets throughout the Gaza Strip," the military said in a statement.
Netanyahu, who arrived in Washington on Sunday for a four-day visit, said he would fly home right after meeting President Donald Trump at the White House on Monday.
The Israeli military said Hamas launched the rocket that destroyed a house in Mishmeret, a village north of Tel Aviv.
There was no claim of responsibility for the early morning attack. The military said Hamas fired the rocket from about 120 km (75 miles) away, making it the longest-range attack from Gaza causing casualties since a 2014 war.
Palestinian security officials said Israeli warplanes attacked targets across the coastal enclave. Palestinian radio stations and Hamas TV played patriotic songs calling for "resistance" against Israel.
There were no immediate reports of casualties in the Gaza Strip. Many targets were likely to have been evacuated in the hours following Netanyahu's initial warning of retaliation shortly after the rocket strike.
Condemning the attack from Gaza, Trump told reporters with Netanyahu at his side that Israel has the "absolute right" to defend itself.
"Israel will not tolerate this. I will not tolerate this," Netanyahu said about the rocket strike. "And as we speak ...Israel is responding forcefully to this wanton aggression." Israel's Magen David Adom ambulance service said it treated seven people in the Israeli village, including an infant, a 3-year-old boy, a 12-year-old girl and a 60-year-old woman who was suffering from blast injuries, burns and shrapnel wounds.
"It just made me feel really unsafe all of a sudden, which is a feeling I'm not used to," said Nitzan Shifrin, a 19-year-old resident of Mishmeret.
The Israeli military said it was assigning two brigades to the Gaza area and some reservists were being called up. Reuters witnesses saw troops moving towards the border, where the military also closed several roads to civilian traffic.
"We are prepared for a wide range of scenarios," chief spokesman Ronen Manelis said.
Israeli towns near Gaza and Tel Aviv, Israel's commercial capital, opened bomb shelters in anticipation of rocket strikes.