GENEVA: UN human rights chief Volker Turk said on Tuesday that "deadly attacks" on civilians around aid distribution sites in the Gaza Strip constituted "a war crime".
Rescuers in the Palestinian territory said Israeli fire targeting civilians near an aid distribution centre in the southern city of Rafah killed 27 people on Tuesday, raising an earlier toll.
It came after a similar incident on Sunday when rescuers said 31 people were killed at the same location, witnesses saying they had been on their way to collect aid.
"Deadly attacks on distraught civilians trying to access the paltry amounts of food aid in Gaza are unconscionable," Turk said in a statement.
"For a third day running, people were killed around an aid distribution site run by the Gaza Humanitarian Foundation. This morning, we have received information that dozens more people were killed and injured."
The US-backed GHF is a recently formed group that Israel has cooperated with to implement a new aid distribution mechanism in Gaza.
The United Nations does not work with the foundation because of concerns that it does not meet core humanitarian principles of neutrality, impartiality and independence.
Turk called for a prompt and impartial investigation into each attack, and for those responsible to be held to account.
"Attacks directed against civilians constitute a grave breach of international law, and a war crime," he said.
"Palestinians have been presented the grimmest of choices: die from starvation or risk being killed while trying to access the meagre food that is being made available through Israel's militarised humanitarian assistance mechanism.
"This militarised system endangers lives and violates international standards on aid distribution, as the United Nations has repeatedly warned."