The UN's Palestinian aid agency on Sunday said all 36 of its shelters in the southern Gaza city of Rafah are "empty" due to Israel's continuing military operation.
The United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) wrote on the social platform X that "thousands of families have been forced to flee."
It said 1.7 million of Gaza's 2.2 million residents are now displaced in the central city of Khan Yunis and surrounding areas.
"The humanitarian space continues to shrink," the agency added.
Aid organizations have repeatedly warned that there is no safe place in the Gaza Strip amid Israel's ongoing operations in the territory, which began in the aftermath of the October 7 attacks by the Palestinian militant group Hamas.
The latest advance by Israeli forces in Rafah has attracted huge international criticism, with aid agencies estimating that around 1 million civilians had taken refuge in the southern city, on the border to Egypt.
The UN's International Court of Justice (ICJ) last week ordered Israel to immediately cease its operations in Rafah, but Prime Minister Benjamin Netanyahu's government has so far failed to heed the ruling.
Israel says Rafah is the last stronghold of Hamas fighters in Gaza, with some of the remaining Israeli hostages from the October 7 attacks believed to be in the network of tunnels under the city.