In Israel, the death toll from Saturday’s shock cross-border assault by Hamas militants rose to 1,200, making it the deadliest attack in the country’s 75-year history, while Gaza officials reported more than 900 people killed as Israel pounded the territory with air strikes.

Hamas said two of its top officials had been killed, while Israel’s military said the bodies of roughly 1,500 Hamas infiltrators had been found.

Prime Minister Benjamin Netanyahu has warned Israel’s military response to Saturday’s attack is only the start of a sustained war to destroy the Islamist group and “change the Middle East”.

Fears of a regional conflagration have surged ahead of an expected Israeli ground incursion into Gaza.

At least 30 people were killed and hundreds wounded as Israel pounded the Gaza Strip with hundreds of air strikes overnight, a Hamas government official said Wednesday.

The strikes destroyed several buildings of the Hamas-linked Islamic University in Gaza City, a university official said.

The Israeli military confirmed it had hit dozens of Hamas targets during the night.

It said fighter jets destroyed “advanced detection systems” that Hamas used to spot military aircraft.

They also hit 80 Hamas targets in the Beit Hanoun area of the northeastern Gaza Strip, including two bank branches used by the Islamist group to “fund terrorism” in the enclave, the military said.

In response to Saturday’s attack, Israel imposed a “total siege” on Gaza, suspending supplies of food, water, electricity and fuel to the already blockaded enclave.

Hamas, which has controlled the Gaza Strip since 2007, is threatening to execute hostages kidnapped in Israel, including young people captured during a music festival where around 270 died.

The balloon attacks sparked nearly two dozen fires in Israel. According to the IDF, the strike which happened early Wednesday morning local time, June 16, targeted Hamas military compounds.

Explosions lit the night sky above buildings in Gaza City as Israeli forces shelled the Palestinian enclave. According to the IDF, the targets were used by Hamas’ Khan Yunis and Gaza Brigades for “terror activities,”.

The unrest comes after an Israeli nationalist march in East Jerusalem that celebrated the 1967 capture of the city.

The military said in a statement “The Hamas terror organization is responsible for all events transpiring in the Gaza Strip and will bear the consequences for its actions. The IDF is prepared for any scenario, including a resumption of hostilities, in the face of continuing terror activities from the Gaza Strip.”

According to the Times of Israel, there were no injuries on both sides of the aisle.

The violence comes just three weeks after a cease-fire halted 11 days of fighting, marking the worst clashes between the IDF and Hamas militants since a small-scale war in 2014.