One million Palestinians have been forced to flee Rafah over the last three weeks in search of safety, according to the United Nations Relief and Works Agency for Palestine Refugees in the Near East.

Heavy bombardment continued in Gaza overnight, including in Tal Al Sultan, where the U.N. main offices in Gaza are located, according to UNRWA Commissioner-General Philippe Lazzarini.

Most of the UNRWA staff could not make it to work as they are packing up and moving. The UNRWA is also running out of medical supplies and basic human medicines, according to Lazzarini.

Just over 200 trucks with humanitarian supplies were picked up in southern Gaza in the last three weeks as needs continue to increase exponentially, Lazzarini said.

-ABC News' Will Gretsky

The United Nations secretary-general has condemned the deadly strike on Rafah "in the strongest terms," saying Antonio Guterres is "heartbroken by the images of the killed and injured," his spokesman, Stephane Dujarric, said in a statement Tuesday.

"The Secretary-General reiterates his demand for an immediate ceasefire and the immediate and unconditional release of all hostages. He recalls the recent orders of the International Court of Justice, which are binding and must be complied with," Dujarric said.

"The humanitarian catastrophe in Gaza is now compounded by the unconscionable prospect of a man-made famine," Dujarric said.

-ABC News' Ellie Kaufman

Israel Defense Forces spokesperson Lt. Col. Nadav Shoshani admitted to a "mishap" in Sunday's Rafah strike that killed 50 Palestinians and injured at least 249 others, saying it was a "tragic incident that shouldn't have happened."

"The outcome is not the outcome we had in mind when this operation started. That's why we're investigating it. It's a tragic event and it's not the way we operate. We are fighting with Hamas terrorists. We are trying to kill them specifically in a very precise way, intelligence based. And that's why we look at this as a tragic incident that shouldn't have happened," Shoshani said.

Over 36,000 Palestinians have been killed in Gaza since Oct. 7.

Israeli Prime Minister Benjamin Netanyahu called the strike a "tragic mishap" on Monday.

"The mishap was the fire that carried out after the targeted attack, and we are looking into why this fire caught on," Shoshani said. "The attack, per se, was according to procedure, with surveillance before the attack, a very precise attack based on intelligence."

-ABC News' Britt Clennett

There are barely any functioning medical facilities in Rafah as the Israel Defense Forces continue its operations, the Palestinian Ministry of Health said Tuesday.

“Both the Indonesian field hospital and the Tal Al-Sultan Clinic in Rafah Governorate have ceased service, leaving only the Tal Al-Sultan Maternity Hospital struggling to survive and continue providing service to patients in Rafah,” according to the ministry.

-ABC News’ Will Gretsky