Israeli forces struck one of the last functioning hospitals in besieged northern Gaza on Thursday, destroying a stockpile of medical supplies that had been delivered to the facility days ago by the World Health Organization, according to Palestinian officials and a spokeswoman for the U.N. agency.

The Israeli military said it was “unaware of a strike” on the facility, Kamal Adwan Hospital, but said it was reviewing the reports. Israeli troops withdrew from the hospital on Monday after a three-day raid during which they arrested most of the medical staff and two children died, Gazan health officials said.

The military said the people it detained in that raid were suspected of being fighters with the militant group Hamas, which led the attack on southern Israel last October that set off the war in Gaza. The medical charity Doctors Without Borders said on Thursday that Dr. Mohammed Obeid, an orthopedic surgeon working for the organization, was among those being held.

“We are extremely alarmed by the detention of our colleague,” the group said. “His work has saved countless lives.”

On Thursday, Israel repeated its assertion that Hamas “has embedded terrorist infrastructure and operates within the Kamal Adwan Hospital.” Gazan officials have denied that claim.

The Gazan health ministry said that the strike on Thursday had significantly damaged “the remaining medicines and medical supplies” at the hospital, in the northern town of Jabaliya. The W.H.O. spokeswoman, Dalia Mohsen, confirmed the health ministry’s account.