An Israeli air strike slammed into a residential building next to the main medical centre in Gaza’s southern city of Khan Younis, killing at least seven people, hospital authorities and witnesses said.

As dust from Wednesday’s strike billowed through a street near Nasser Hospital, people were running in all directions – some rushing towards the destruction and others away. Later, civil defence first responders and bystanders picked their way across chunks of cement and twisted metal, searching for people who might have been buried.

Nasser Hospital sits in the western part of the city. There have been repeated attacks on Khan Younis, Rafah and al-Mawasi in the south of the enclave, all of which had previously been designated as humanitarian “safe zones” by Israel.

The Israeli military’s evacuation order this week for Khan Younis, Gaza’s second-largest city, affected about 250,000 people, according to the United Nations.

Displaced families ordered out of eastern Khan Younis have struggled to find places to live in overcrowded shelters and open areas in the western parts of the city. Wednesday’s air strike hit an area that also includes a school-turned-shelter for displaced people, many of whom are living in makeshift tents.

“We were sitting in this tent, three people, and we were surprised by the rubble and dust,” said Jalal Lafi, who was displaced from Rafah.

“The house was bombed without any warning, hit by two missiles in a row, one after another,” he said, looking over his shoulder at the rubble, his hair and clothes covered in grey soot.

Andrea De Domenico, the head of the UN Office for the Coordination of Humanitarian Affairs (OCHA) in the occupied Palestinian territories, said Gaza is “the only place in the world where people cannot find a safe refuge, and can’t leave the front line”. Even in so-called safe areas there are bombings, he told reporters on Wednesday.

An Israeli air strike on Tuesday killed a prominent Palestinian doctor and eight members of his extended family hours after they complied with military orders to evacuate their home and moved to the Israeli-designated safe zone.

The European Hospital in Khan Younis has been put out of service after Israeli forces bombarded several areas there and medical personnel were forced to evacuate patients and move what was left of devices and equipment, the Palestinian Wafa news agency reported.