"The images from the camp are horrific and point to no apparent change in the methods and means of warfare used by Israel that have already led to so many civilian deaths," Volker Turk said in a statement.

He voiced his "horror at the further loss of civilian life in Gaza", the statement said.

Israel has faced a wave of international condemnation over Sunday's strike on the Al Hashash area in Rafah, which according to Gaza officials killed 45 people when the strike set off a fire that ripped through a tent city for displaced Palestinians.

Israel launched the attack hours after Hamas unleashed a barrage of rockets at Tel Aviv and nearby areas which sent Israelis running for bomb shelters. Most were intercepted by air defences.

Israel's military said the southern Rafah area had targeted and killed two senior Hamas operatives. It also sparked a fire that Palestinians and many Arab countries condemned as a "massacre".

"Sunday's strike underscores once again that there is literally no safe place in Gaza", Turk said.

He noted that the military had announced it would investigate.

But, he said, "what is shockingly clear is that by striking such an area, densely packed with civilians, this was an entirely predictable outcome".

"It is crucial that such reviews lead to accountability and changes in policy or practices."

The UN High Commissioner for Human Rights called on Israel to respect an International Court of Justice order issued Friday to halt the Rafah offensive.

He reiterated a call on all parties establish a ceasefire, stressing their obligation to protect civilians.

"Israel must take immediate steps to protect civilians, and ensure they have access to essential humanitarian assistance, and release all those detained arbitrarily," Turk said.

He insisted that "Palestinian armed groups must stop the firing of rockets which are inherently indiscriminate and in clear violation of international humanitarian law".

"They must also unconditionally release all hostages at once," he said.

The Gaza war broke out when Hamas launched its October 7 attack on Israel that left more than 1,170 people dead, mostly civilians, according to an AFP tally based on Israeli official figures.

Militants also took 252 hostages, 121 of whom remain in Gaza. The Israeli army says 37 of those still missing are dead.

Israel's retaliatory offensive has killed at least 36,050 people in Gaza, mostly women and children, according to the Hamas-run territory's health ministry.