At least 150 people are reported killed and 1,100 wounded in Israel after the Palestinian militant group Hamas launched its biggest attack in years.
Dozens of gunmen from Gaza infiltrated southern Israeli communities after dawn under the cover of heavy rocket fire.
They have taken both Israeli soldiers and civilians hostage, and some have been brought back to Gaza.
Israel has responded with a wave of air strikes on Gaza that have killed 232 people and wounded 1,600, medics say.
Israeli Prime Minister Benjamin Netanyahu said Israel was “at war” and vowed that Hamas, which rules Gaza, would “pay an unprecedented price”.
The Israeli military has mobilised tens of thousands of reservists and is now expected to launch a ground operation in Gaza.
How did Israeli intelligence fail to stop major attack?
This is one of the most serious escalations in the Israel-Palestinian conflict in years.
The attack by Hamas saw fighters cross the perimeter fence at just after dawn. At the same time, barrages of rockets were launched from Gaza – some reaching as far as the cities of Tel Aviv and Jerusalem.
How the gunmen managed to penetrate one of the most heavily fortified borders in the world is unclear.
The Israeli military has said dozens of fighter jets are carrying out air strikes on Hamas sites in Gaza, and it has hit 17 Hamas military compounds. It also said it has mobilised tens of thousands of reservists.
Israeli bombs destroyed an 11-story tower in downtown Gaza City which houses Hamas radio stations in the rooftop.
Medical aid group Medecins Sans Frontieres said a nurse and an ambulance driver were killed in Israeli strikes on two hospitals in Gaza.
Reuters news agency reported Israel’s energy minister, Israel Katz, as saying that Israel would cut off Gaza’s electricity supply.
Map showing Gaza and southern Israel and where Hamas militants have infiltrated
The rocket barrages from Gaza – the biggest attack by Hamas on Israel in years – began just after dawn on Saturday, the Jewish Sabbath and the day of the festival of Simchat Torah.
As sirens sounded across Israel, the Israel Defence Forces (IDF) announced that “terrorists” had infiltrated Israeli territory “in a number of different locations”.
People in towns close to Gaza have been calling in to Israeli news stations saying they were trapped in their homes, as militants entered their towns and villages.
In the town of Sderot, only 1.6km (1 mile) from Gaza, videos posted online appeared to show a group of heavily armed Palestinian militants driving around in a pick-up truck and exchanging fire with Israeli forces.
