Israel on Sunday blocked aid flowing into Gaza, where a six-week truce enabled the entry of vital food, shelter and medical assistance, prompting the UN to call for an immediate restoration of humanitarian assistance.

The Israeli decision came as talks on a truce extension appeared to hit an impasse, after the ceasefire's 42-day first phase drew to a close.

Truce mediators Egypt and Qatar accused Israel of blatantly violating the ceasefire deal by halting the aid.

Early on Sunday, Israel had announced a truce extension until mid-April that it said United States Middle East envoy Steve Witkoff had proposed.

But Hamas has repeatedly rejected an extension, instead favouring a transition to the truce deal's second phase that could bring a permanent end to the war.

With uncertainty looming over the truce, both Israel and Palestinian sources reported Israeli military strikes in the Hamas-run Gaza Strip, whose health ministry reported at least four people killed.

Hamas, whose October 7, 2023 attack on Israel triggered the fighting, said the "decision to suspend humanitarian aid is cheap blackmail, a war crime and a blatant coup against the [ceasefire] agreement".

The Egyptian foreign ministry accused Israel of using starvation as "a weapon against the Palestinian people", comments echoed by Qatar which said it "strongly condemns" Israel's decision.

Saudi Arabia, which has rejected any talk of normalising ties with Israel without a Palestinian state, condemned the aid block as "a tool of blackmail and collective punishment".

Jordan said Israel's action "threatens to reignite" fighting in Gaza.

UN chief Antonio Guterres called for "humanitarian aid to flow back into Gaza immediately".

The European Union condemned what it called Hamas's refusal to accept the extension of the first phase, and added that Israel's subsequent aid block "risked humanitarian consequences".

Brussels called for "a rapid resumption of negotiations on the second phase of the ceasefire". (AFP)