Israel Defense Forces troops began attacking Hamas facilities in the Gaza Strip on Monday evening, a little over 12 hours after a rocket attributed to the terror group hit a home in the center of the country, wounding seven people.
The military confirmed the start of the operation at around 5:45pm, saying that its forces were "striking Hamas targets throughout the Gaza Strip."
The wave of attacks by Israeli warplanes in the Gaza Strip on Monday evening were just the first stage of what will be a broad operation, the IDF spokesman told Ynet.
"We are just at the beginning," Brig. Gen. Ronen Manelis said. "A large attack is planned. I think that Hamas understands this is a significant strike (following) a serious incident, and ultimately, this is a price that Hamas has been accruing for the past year."
At around 7pm, the army said its warplanes had attacked a three-story building in central Gaza that served as the secret headquarters of Hamas, housing the terror group's security and general branches.
The expected retaliation was not long in coming. Air raid sirens began to sound in the Eshkol Regional Council, close to the Gaza border, warning of rocket fire from Gaza, at around 8pm.
Meanwhile, city councils across Israel, including in Tel Aviv, Rishon Lezion, Be'er Sheva, Ashkelon and Kiryat Malachi opened their public bomb shelters in anticipation of rocket strikes.
Ashkelon council said Monday evening that its schools would be closed Tuesday, and it was banning public gatherings of more than 300 people, the Walla news website reported.
The barrage began as Prime Minister Benjamin Netanyahu was meeting with President Donald Trump at the White House. Netanyahu, who was in the US for the annual AIPAC conference, cut his trip short and was to return home immediately after his meeting with the president.
Speaking from the White House, Netanyahu said that Israel would not tolerate rocket attacks on its territory, and would do whatever it must to protect its people.
Palestinians in Gaza said that the IDF had attacked Hamas' large "Ashkelon" position as well as targets along the coast in the northern Strip, which is under the control of Hamas' naval force.
Gazans also reported attacks in the Rafah area of the southern Strip, close to the border with Egypt.
Yaakov Amidror, a former national security adviser to Netanyahu, said a mild response was not an option.
"It will be something on a bigger scale," he said.
"He doesn't want a war before elections, but they put him in a corner," he added. "After three missiles reaching the heart of Israel, the chance of a big escalation including a ground offensive, is very high."
In Beirut, Iranian-backed Lebanese terror group Hezbollah said its leader, Hassan Nasrallah, met Monday with a Hamas delegation led by miliary leader Saleh Arouri. Hezbollah said they discussed the Gaza situation and "Israeli aggression."
Hamas leader Ismail Haniyeh said the group would respond if Israel retaliated too forcefully to the rocket strike.
In a written statement, Haniyeh said the Palestinian people "will not surrender" and its militant factions "will deter the enemy if it exceeds the red lines."
The attacks followed a day of preparations by the IDF, closing roads and halting agricultural work near the security fence that runs along the border with the Gaza Strip.
The IDF's Gaza Division said it would block routes and areas on the Israeli side of the fence and requested that residents "follow security instructions as long as necessary."
Earlier in the day, the army deployed infantry and armored corps units to the Gaza border, and began calling up reservists from Iron Dome and intelligence units.
Israel said that Hamas, which rules the Gaza Strip, was behind the rocket launch, and warned it would "respond forcefully" to a "criminal attack."
IDF Spokesman Ronen Manelis told a press briefing Monday morning that the rocket was fired from the Rafah area of southern Gaza - a range of 120 kilometers. According to the IDF, the rocket that struck the home is a self-manufactured Hamas rocket.
"The rocket fire was carried out by Hamas from a Hamas position. We see Hamas as being responsible for everything that happens in the Gaza Strip," the army said.
The terror organization seized power in Gaza in 2007, and has ruled the Strip ever since.