DEFIANT Hamas leaders last night warned they would kill a hostage for each new Israeli attack.

The chilling threat came as Israel launched a revenge blitz on the terror group, with the first of 300,000 troops arriving on the Gaza Strip border ready for a ground assault.

The country’s air force struck 2,400 terror targets after Hamas slayed civilians and seized hostages in a shock weekend attack dubbed Israel’s 9/11.

As the death toll on both sides last night hit around 1,500, Israel’s PM Benjamin Netanyahu vowed: “This is only the beginning.”

Hamas chiefs countered by warning they will kill a hostage for every attack on civilians in Gaza, and broadcast their deaths.

The group’s armed wing spokesman Abu Ubaida said: “From this moment on, we announce that every targeting of our people who are safe in their homes without prior warning will be met, with regret, by the execution of one of our enemy’s civilian hostages.

“And we will urgently broadcast this with audio and video.”

Israel has ordered a total siege of Gaza in a bid to bring Iranian-backed Hamas to its knees, cutting off water, electricity, food and fuel.

More than 130,000 Palestinians have fled their homes as air strikes pound the crowded enclave, with at least 560 already dead.

Around 900 Israelis are also believed to have been killed, with Hamas terrorists reportedly beheading soldiers and desecrating their bodies on video.

Mr Netanyahu denounced them as worse than Islamic jihadists IS, and vowed to destroy them in the coming “war”.

He said: “What we will do to our enemy over the next few days will echo for generations.

“Any place from which Hamas operates will turn into rubble.”

PM Rishi Sunak chaired a Cobra meeting yesterday amid concern for 60,000 Brits in Israel and Gaza, with ten already feared dead.

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Home Secretary Suella Braverman vowed to outlaw public shows of support for Hamas in the UK.

She said: “The barbaric attack on Israel by Hamas terrorists who have massacred civilians and kidnapped the most vulnerable is truly sickening. The UK stands unequivocally with Israel in her fight against this evil.”

The US also pledged “rock solid” support for Israel, and dispatched an aircraft carrier strike group to the eastern Mediterranean.

After breaking through the border with explosives and diggers at daybreak on Saturday, 1,000 Hamas gunmen rampaged for hours.

Partygoers at a festival were among those targeted.

Some fighters are believed to still be inside Israel.

Militants also launched 4,400 rockets as hostages were taken to Gaza, including children and a Holocaust survivor in a wheelchair.

Israeli Defense Forces chief Herzi Halevi declared it was in a “state of war” and vowed revenge.

He said: “This is murderous terrorism. We are attacking, pushing back, and striking everyone who took part in it.”

The Israeli military has more than 2,000 tanks, 600 planes and 8,000 elite commandos — vastly outnumbering Hamas.

Tanks and drones have been deployed to guard breaches in the border fence while 300,000 reservists have been mobilised.

Yesterday, militant group Hezbollah fired rockets into northern Israel from Lebanon in response to its members being killed in shelling.