Israel's attack on Hamas militants in Rafah has left 800,000 people “forced to flee”, the United Nations said on Saturday.
Griffiths said the military action in southern Gaza City was exactly as we feared, with fuel, food and medicine running out.
“And we all said very clearly, that the Rafah operation is a disaster in humanitarian terms, a disaster for the already displaced people in Rafah.
This is now their fourth or fifth displacement,” he said.
With major land crossings closed, some relief supplies began arriving this week via a temporary, floating ferry built by the United States.
Griffiths said the maritime operation had “started to bring aid in some trucks” but cautioned that “it is not a replacement for land routes”.
The war began after Hamas' unprecedented attack on Israel on October 7, resulting in the deaths of more than 1,170 people, mostly civilians, according to an AFP tally based on Israeli official figures.
Israel's counteroffensive against Hamas has killed at least 35,386 people in Gaza, mostly civilians, according to figures provided by the Hamas-run territory's health ministry.
Of the 252 people taken hostage by Israel during the October 7 attack, 124 remain in Gaza, 37 of whom the military says are dead.
On Thursday, the Arab League called for the deployment of UN peacekeeping forces in the Palestinian territories and an international conference to resolve the Palestinian issue on the basis of a two-state solution.
Griffiths said the 22-member bloc's statement in Manama was “very important because it focused on the future”.