The Israeli military said Friday it had begun airstrikes in the Gaza Strip in response to a rocket attack on Tel Aviv - which was the first time the city, some 50 miles north of Gaza, was targeted by rocket fire since a 2014 war against Gaza militants.
That salvo caused no casualties or damage, missing built-up areas.
But it rattled Israeli nerves ahead of an April 9 election in which Prime Minister Benjamin Netanyahu is seeking a fifth term on the strength of his national security and diplomatic credentials.
The Israeli military has concluded that the militant Hamas group of Gaza fired two rockets toward the Israeli coastal city of Tel Aviv.
Palestinian media also reported multiple strikes on Gaza City and at a target in Beit Lahiya in northern Gaza. One was reported to have been intercepted by the Iron Dome missile defense system while another one is said to have fallen in open territory.
The heads of Gaza's ruling Hamas terrorist organization evacuated all of its headquarters in the enclave in anticipation of a likely military response to the attack by the Israel Defense Forces later in the evening. There have been several smaller rounds of fighting since, reined in by Egyptian and United Nations mediations.
"This was basically a surprise", military spokesman Brigadier-General Ronen Manelis told Israel Radio.
The usual suspects - Hamas, the Popular Resistance Committees and the Iran-backed Palestinian Islamic Jihad - each denied their respective terror groups were behind the projectile attacks.
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"The Hamas organisation is the main organisation in the strip. It is responsible for what happens within the Strip and what emanates from it".
Hamas and PIJ told Egyptian security officials who were in the Strip to discuss a long-term truce that they were not responsible for the rockets, Al-Jazeera reported.
Harsh sirens rang out across the streets as citizens were warned of the first missile attacks since 2014.
Israeli analysts speculated that Palestinian militants opposed to any deal between Hamas and Israel were behind the launchings.
Residents reported hearing a loud explosion during the rocket attacks on Tel Aviv.
Netanyahu, who doubles as Israel's defence minister, was conferring with military and security staff, his office said.
He said that while "rogue factions" were behind recent Gaza "provocations", it "did not exempt Hamas" of responsibility.