Israel has blocked the entry of all humanitarian aid into Gaza as it demands Hamas agree to a US plan for a ceasefire extension.

The first phase of the ceasefire expired on Saturday. Israeli Prime Minister Benjamin Netanyahu’s office said Hamas had so far refused to accept a temporary extension under a proposal by Donald Trump’s envoy, Steve Witkoff.

A Hamas spokesman said blocking supplies to Gaza was “cheap blackmail” and a “coup” on the ceasefire agreement and urged mediators to intervene.

The Palestinian group wants phase two of the deal to go ahead as originally negotiated, with the release of hostages and Palestinian prisoners and the withdrawal of Israeli forces from Gaza.

It previously said it would not agree to any extension of phase one without guarantees from US, Qatari and Egyptian mediators that phase two would eventually take place.

A statement from Netanyahu’s office said: “With the end of Phase 1 of the hostage deal, and in light of Hamas’s refusal to accept the Witkoff outline for continuing talks – to which Israel agreed – Prime Minister Netanyahu has decided that, as of this morning, all entry of goods and supplies into the Gaza Strip will cease.

“Israel will not allow a ceasefire without the release of our hostages. If Hamas continues its refusal, there will be further consequences.”

The Hamas spokesman said: “Netanyahu’s decision to stop aid going into Gaza once again shows the ugly face of the Israeli occupation… The international community must apply pressure on the Israeli government to stop starving our people.”

Late last night, Netanyahu’s office said Israel had agreed to a US proposal for the ceasefire to continue for about six weeks during the Muslim Ramadan and Jewish Passover periods.

If, at the end of this period, negotiations reached a dead end, Israel would reserve the right to go back to war.

US envoy Witkoff has not made his proposal public. According to Israel, it would begin with the release of half of all the remaining living and dead hostages.

Witkoff is said by Israel to have proposed the six-week extension after becoming convinced that more time was needed to try to bridge the differences between Israel and Hamas on conditions for ending the war, according to the earlier statement from Netanyahu’s office.

Israel would immediately start negotiations on this if Hamas changed its position on the six-week ceasefire extension, Netanyahu’s office said.

Aid agencies confirmed that no aid trucks had been allowed into Gaza on Sunday morning.

“Humanitarian assistance has to continue to flow into Gaza. It’s very essential. And we are calling all parties to make sure that they reach a solution,” Antoine Renard from the World Food Programme (WFP) told the BBC.

Thousands of trucks have been entering the Gaza Strip each week since the ceasefire was agreed in mid-January. Aid agencies have managed to store supplies, which means there is no immediate danger to the civilian population from this morning’s Israeli decision.

Egypt – one of the mediators between Israel and Hamas – has called for the previously agreed upon ceasefire deal to be implemented in full. The Egyptian foreign minister said his country would present a plan to rebuild Gaza without displacing its people at an emergency Arab summit on Tuesday.

Also on Sunday, medics said four people had been killed in Israeli strikes on Gaza. The Israeli military said it had attacked people who were planting an explosive device in the north of the territory.

The first phase of the ceasefire that came into force on 19 January expired on Saturday.

It halted 15 months of fighting between Hamas and the Israeli military, allowing the release of 33 Israeli and five Thai hostages for about 1,900 Palestinian prisoners and detainees.

But negotiations on phase two, including the release of all remaining living hostages and the withdrawal of Israeli troops from Gaza, have barely begun.

There are believed to be 24 hostages alive, with another 39 presumed to be dead.

Hamas carried out an unprecedented attack on Israel on 7 October 2023, killing about 1,200 people and taking another 251 hostage.

Israel responded with an air and ground campaign in the Gaza Strip, during which at least 48,365 people have been killed, according to the territory’s Hamas-run health ministry.