Israeli strikes on Gaza have killed more than 250 people since Thursday morning, local health authorities said on Friday, one of the deadliest phases of bombardment since a truce collapsed in March, with a new ground offensive expected soon.

Aid groups and U.N. investigations have accused Israel of aiming to destroy Gaza’s health infrastructure. Israel says it is forced to strike hospitals it says are used by Hamas for military purposes.

Hospitals and health officials say Israeli airstrikes have pounded northern and southern Gaza and killed at least 70 people. The dead include almost two dozen children.