The United Nations Relief and Works Agency for Palestine Refugees (UNRWA) said on Sunday that more than 300 people were killed in Israeli bombings targeting 180 of its facilities in the Gaza Strip.
The Director of Media and Communications at the UN agency, Juliette Touma, told the BBC that "about 1.4 million Palestinians have been displaced due to the Israeli raids and are living in UNRWA facilities across Gaza."
"Our facilities have become completely full, so people have started sleeping outdoors," she added.
In a separate post, the UN agency said: “While the world is crowded with New Year's celebrations, the streets of southern Gaza Strip are crowded with displaced people.”
Since October 7, Israel's devastating war on Gaza has killed at least 21,822 people and injured 56,451.
The Israeli attacks have resulted in massive destruction of infrastructure and an unprecedented humanitarian catastrophe.
Humanitarian organisations have described the situation in Gaza as "unbearable," with people living in "hellish conditions" after Israel left "no safe zones" for civilians to take refuge in. Nearly all the territory's 2.4 million people have been displaced.
UNRWA had earlier announced that 142 of its staff members were killed in Gaza by Israeli strikes.
UNRWA was set up in 1949 to provide relief and assistance to Palestinians who were made refugees when Israel was established, in an event known as the Nakba.