The World Health Organization on Friday voiced concern over the fate of the head of Gaza City's Al-Shifa hospital, who has been detained by Israeli forces.
In a statement the WHO said that the head of the biggest hospital in the besieged Palestinian territory had been arrested on Wednesday along with five other health workers, while they were taking part in a UN mission to evacuate patients.
"Three medical personnel from the Palestine Red Crescent Society and three from the Ministry of Health were detained," the WHO said.
Since then two of the six have reportedly been released, but "we do not have information about the well-being of the four remaining health staff, including the director of Al-Shifa hospital," the statement added.
The UN agency called for "their legal and human rights to be fully observed during their detention".
Hospital director Mohammad Abu Salmiya has been frequently quoted by international media about the conditions inside Al-Shifa, a major target of the Israeli ground offensive on the Gaza Strip.
The Israeli army, which besieged and raided the hospital last week, has claimed that Hamas fighters used a tunnel complex beneath the facility in Gaza City to stage attacks.
Hamas and hospital officials have repeatedly denied the claims and no convincing evidence has been presented.
On Thursday the Israeli army announced it had arrested the hospital chief, along with a department head.
According to the WHO statement, the organisation has carried out three missions to al-Shifa in the space of a week, on one occasion managing to evacuate 31 babies from the hospital.
The Israeli siege and raids on Al-Shifa have caused the deaths of dozens of patients, including babies. Staff have had to dig mass graves for those who died.
Israel's indiscriminate war on the Gaza Strip, which has targeted residential areas, schools, and places of worship as well as hospitals has killed an estimated 15,000 people, mostly women and children.
During the third mission, on Wednesday, which was carried out in cooperation with the Palestinian Red Crescent, 151 people were evacuated, including patients, their relatives and healthcare workers, according to the WHO.