The Israeli military has bombed targets in overcrowded Rafah, hours after United States officials warned Tel Aviv against expanding its ground offensive to the southern city, where more than half of the Gaza Strip’s 2.3 million people have sought refuge.

US President Joe Biden called Israel’s conduct in the war “over the top” in the harshest criticism yet from Washington of its close ally amid concerns about the soaring civilian death toll in the enclave.

With the war now in its fifth month, Israeli ground forces are still focusing on the city of Khan Younis, just north of Rafah, but Israeli Prime Minister Benjamin Netanyahu has repeatedly said Rafah will be next, creating panic among hundreds of thousands of displaced people there.

Netanyahu has ordered soldiers to prepare for a ground entry into Rafah, alarming Egypt, which has said any ground operation in the Rafah area or mass displacement across the border would undermine its 40-year-old peace treaty with Israel. The mostly sealed Gaza-Egypt border is also the main entry point for humanitarian aid.

An estimated 1.2 million people have fled to Rafah, heeding Israeli evacuation orders ahead of the military’s continuously expanding bombardments and ground offensive. Evacuation orders now cover two-thirds of the besieged territory although an estimated 300,000 Palestinians remain in the northern half of Gaza, which civilians were ordered to leave early in the war.

Even in areas Israel had declared “safe zones”, such as Rafah, it routinely launches air strikes against what it says are Hamas targets. It holds the Palestinian group responsible for civilian casualties in Gaza, saying it operates from civilian areas.