At least 12 Palestinians, including a five-year old girl and a woman, were killed and 80 injured in Israeli air strikes in the Gaza Strip, the Palestinian Health Ministry said.
Israel on Friday said it had launched a special operation against the Palestinian Islamic Jihad militant group, killing one of its senior commanders in a daytime air-strike on a high-rise building in Gaza City.
Israeli aircraft struck in Gaza again on Saturday, and Palestinian militants fired rockets at Israeli cities as fighting ran into a second day, ending more than a year of relative calm along the border.
The death toll rose to 12 after two people were killed in Khan Yunis in the southernn Gaza Strip on Saturday, health authorities in the coastal enclave said.
Islamic Jihad said a Gaza commander, Tayseer Al Jabari, was among those killed on Friday. The Israeli army confirmed Al Jabari had been the target of the strikes.
“Tayseer Al Jabari was responsible for multiple terrorist attacks against Israeli civilians. The [Israel Defence Forces] will continue to defend Israel against the threat of terrorism,” the Israeli army said on Friday.
An explosion could be heard in Gaza City, where smoke poured out of the seventh floor of a multistorey building on Friday afternoon.
Further Israeli strikes east of Gaza City late on Friday injured five civilians including three children, the Palestinian Wafa news agency reported.
Palestinian militants launched a barrage of rockets hours after the initial Israeli strikes, triggering air raid sirens in central and southern Israel. Islamic Jihad claimed to have fired 100 rockets.
Images broadcast by Israeli television stations appeared to show a number of rockets being shot down by air defence systems.
The Israeli army said on Saturday that it conducted overnight raids in the West Bank and arrested 20 people, including 19 Islamic Jihad members.
Egypt said it was conducting intensive contacts with the aim of containing the situation in Gaza, bringing calm and protecting lives and property, according to a brief statement by the Foreign Ministry.
UN Middle East peace envoy Tor Wennesland said he was "deeply concerned", warning that the escalation was "very dangerous".
“The Israeli government will not allow terrorist organisations in the Gaza Strip to set the agenda in the area adjacent to the Gaza Strip and threaten the citizens of the state of Israel,” Prime Minister Yair Lapid said in a statement.
“Anyone who tries to harm Israel should know: we will find you.”
Defence Minister Benny Gantz approved an order to call up 25,000 reserve soldiers if needed.
The violence poses an early test for Mr Lapid, who assumed the role of caretaker prime minister before elections in November.
He has experience in diplomacy, having served as foreign minister in the departing government, but his security credentials are thin.
The Palestinian Authority condemned the Israeli “aggression” in the Gaza Strip, demanded an immediate halt to the strikes and said it held Israel's forces responsible for this “dangerous escalation”.
It called on the international community to demand Israel stop its attacks and to provide international protection for the Palestinian people.
The strikes came after Israel arrested Bassam Al Saadi, a senior leader of the Palestinian group Islamic Jihad, during a raid in the occupied West Bank city of Jenin this week.
Israel later closed off all Gaza crossings and some nearby roads over fears of retaliatory attacks from the group, which wields strong influence in the enclave.
“The enemy has begun a war against our people and against us and we will defend ourselves and our people,” Islamic Jihad said.
Israel and the Hamas fought four wars since the militant group seized power in the coastal strip from rival Palestinian forces in 2007. The most recent was in May 2021 and tension again soared this year following a wave of attacks inside Israel, near-daily military operations in the West Bank and clashes at a Jerusalem holy site.
Last month, Israel launched strikes on a Hamas position in the Gaza Strip after bullets were fired from the Palestinian enclave, the Israeli military said on Tuesday.
Mr Gantz visited communities near Gaza on Friday, saying authorities were preparing “actions that will remove the threat from this region”, without elaborating.
“We will operate with internal resilience and external strength in order to restore routine life in Israel’s south,” he said. “We do not seek conflict, yet we will not hesitate to defend our citizens, if required.”
Islamic Jihad leader Ziad Al Nakhalah, speaking to Al Mayadeen TV network, said “we are starting the fight, and the fighters of the Palestinian resistance have to stand together to confront this aggression”. He added that there would be “no red lines” in the confrontation and blamed the violence on Israel.
Hamas spokesman Fawzi Barhoum said “the Israeli enemy, who started the escalation against Gaza and committed a new crime, must pay the price and bear full responsibility for it”.