Hamas has claimed that at least 13 Israeli and foreign hostages held by the military in the northern Gaza Strip have been killed in Israeli air strikes.
"Thirteen prisoners... including foreigners" were killed in five locations targeted by Israeli fighter jets, the Ezzedine al-Qassam Brigades said in a statement.
Earlier, Israel Defense Forces (IDF) had said that Hamas had taken around 150 people, including women and foreign nationals, as hostages following the shocking attack on Saturday.
The Ezzedine al-Qassam Brigades had warned that "every targeting of our people without warning will be met with the execution of one of the civilian hostages."
Israel has been pounding Gaza with aerial bombardments at unprecedented scales in response to the attack on Saturday.
Hundreds of Hamas gunmen attacked Israel from Gaza at dawn on Saturday, on the Jewish holiday of Simchat Torah.
The Iran-backed Islamists said they fired around 5,000 rockets into Israel 50 years and one day after the start of the 1973 Arab-Israeli war.
The air strikes have claimed more than 1,530 lives -- 500 of them children, according to the health ministry in Gaza.
Israel's Defence Minister Yoav Gallant on Monday ordered a "complete siege" of Gaza Strip, which is home to about 2.4 million people and has been blockaded since 2006, meaning "no electricity, no food, no water, no gas".
Meanwhile, Israel on Friday gave Palestinians 24 hours to leave Gaza City ahead of an expected ground offensive.
IDF confirmed on Friday that it had called on Gaza City residents to move "to the area south of the Wadi Gaza", which is just below Gaza City in the 40-kilometre-long territory.
"In the following days, the IDF will continue to operate significantly in Gaza City and make extensive efforts to avoid harming civilians," the army said. "Hamas terrorists are hiding in Gaza City inside tunnels underneath houses and inside buildings populated with innocent civilians."
With the ground offensive in Gaza imminent, Saleh Al-Arouri, deputy chief of Hamas politburo, told Al Jazeera that before Hamas unleashed its assault on Israel, it had a stronger defence plan than its attack plan.
Palestinian militant official Abu Abdallah said Gaza's fighters were ready.
"Planes do not determine a battle. Many fighters would prefer to face tanks and forces on the ground, armed by the developed capabilities built up over years," he said.
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