Overnight strikes by Israel killed at least 55 people across the Gaza Strip, hospital officials said on Thursday, a day after senior government officials said Israel would seize large areas of Gaza and establish a new security corridor across the Palestinian territory.

Israel has vowed to escalate the nearly 18-month war with Hamas until the militant group returns dozens of remaining hostages, disarms and leaves the territory. Israel has imposed a month-long halt on all imports of food, fuel and humanitarian aid that has left civilians facing acute shortages as supplies dwindle.

Officials in Khan Younis, in the southern part of the strip, said the bodies of 14 people had been taken to Nasser Hospital — nine of them from the same family. The dead included five children and four women. The bodies of another 19 people, including five children aged between 1 and 7 years and a pregnant woman, were taken to the European hospital near Khan Younis, hospital officials said.

The Israeli military ordered the residents of several areas — Shujaiya, Jadida, Turkomen and eastern Zeytoun — to evacuate on Thursday, adding that the army “will work with extreme force in your area”. It said people should move to shelters west of Gaza City.

On Wednesday, Prime Minister Benjamin Netanyahu announced Israel was establishing a new security corridor across the Gaza Strip to pressure Hamas, suggesting it would cut off the southern city of Rafah from the rest of the Palestinian territory.

Netanyahu referred to the new axis as the Morag corridor, using the name of a Jewish settlement that once stood between Rafah and Khan Younis, suggesting it would run between the two southern cities.