Hospitals in Gaza are facing dire conditions as much-needed fuel is running dry and staff try to operate amid overcrowding, disintegrating sanitation and threats from Israel.

Health officials in the Hamas-run Gaza Strip report 18 out of 35 hospitals are no longer operational, according to new numbers released Tuesday.

At least 71% of all primary care facilities across Gaza have been shut down due to damage or lack of fuel, the officials said.

The United Nations says an estimated 117,000 displaced people, in addition to patients and hospital staff, are in the hospitals still operational in Gaza City and northern Gaza. Israel has dropped leaflets and sent messages telling people to leave these areas as troops close in.

"It's a health catastrophe right now what is happening in Gaza," Tarik Jasarevic, a spokesperson for the World Health Organization, told NPR.