Israeli tank shelling and airstrikes have killed 18 people, including four children, in Gaza and Israel has halted the evacuation of patients through the Rafah border crossing, Palestinian officials have said.

The Israeli military said it fired on Gaza after a gunman shot at Israeli soldiers and seriously injured a reservist.

The strikes targeted Gaza City and the southern city of Khan Younis. A Gazan health official said Israel had also halted the passage of patients through the Rafah border crossing to Egypt, two days after it had reopened, allowing a trickle of Palestinians to cross for the first time in months.

The Red Crescent said patients had arrived at a hospital in Khan Younis in preparation for crossing Rafah for treatment, only to be informed that Israel had postponed the evacuations.

“They called the patients and said today there is no travel at all, the crossing is closed,” Raja’a Abu Teir, a Palestinian patient who was expecting to be evacuated,said at the hospital, where several patients were waiting in ambulances.

The Israeli military agency that controls access to Gaza, Cogat, said on Wednesday that the Rafah crossing remained open, but it had not received the necessary coordination details from the World Health Organization to facilitate the crossing.

The WHO did not immediately respond to a request for comment.

Reopening the crossing was one of the requirements under the October ceasefire that set out the first phase of US president Donald Trump’s plan to stop fighting between Israel and Palestinian Hamas militants.

Sixteen patients from Gaza and 40 of their escorts crossed into Egypt on Tuesday, medics in Gaza said.

A Hamas police source said at least 40 people crossed from Egypt to Gaza late on Tuesday.

In January, Trump declared the start of the second phase of the ceasefire in which the sides would negotiate the shattered territory’s future governance and reconstruction.

Key issues such as the withdrawal of Israeli forces from the over 50% of Gaza they occupy and the disarmament of Hamas remain unresolved, while the fragile ceasefire has been marked by near-daily violence.

Since the start of the ceasefire, Israeli fire has killed at least 530 people, most of them civilians, according to Gaza health officials. Palestinian militants have killed four Israeli soldiers in the same period, according to Israeli authorities.