Israel's strikes on the Gaza Strip have led to an "unprecedented human catastrophe" in the Palestinian territory, the United Nations agency supporting Palestinian refugees said Sunday.

"Not one drop of water, not one grain of wheat, not a liter of fuel has been allowed in the Gaza Strip for the last eight days," Philippe Lazzarini, commissioner general of UNRWA, told journalists.

"Raise the alarm that as of today, my UNRWA colleagues in Gaza are no longer able to provide humanitarian assistance as I speak," Lazzarini said.

"In fact, Gaza is being strangled and it seems the war right now has lost its humanity," he continued.

"If we look at the issue of water, we all know water is life and Gaza is running out of water and Gaza is running out of life."

Israel's Energy Minister Israel Katz earlier said water supply was resuming to southern Gaza after talks between Prime Minister Benjamin Netanyahu and US President Joe Biden.

"This will push the civilian population to the southern (part of the) Strip," Katz said in a statement, a week after Israel had stopped supplying water to the entire territory as part of a "complete siege" on the Palestinian enclave.

US National Security Advisor Jake Sullivan earlier said that Israel told him it had turned the water supply back on in southern Gaza.

The municipality of Beni Suheila in southern Gaza confirmed that the water supply had resumed to the village.

At least 2,670 people have been killed in the Gaza Strip in a blistering air assault launched by Israel last week after Hamas carried out a bloody attack on Israel that left more than 1,400 people dead.

An estimated one million people have been displaced in the first seven days of the conflict in Gaza, UNRWA said earlier on Sunday.

"The number is likely to be higher as people continue to leave their homes," UNRWA director of communications Juliette Touma told AFP.