Hamas militants attacked Israel's main crossing point for delivering humanitarian aid into the Gaza Strip on Sunday, dealing a blow to the ongoing crease-fire efforts that appear at an impasse with both sides blaming each other.

The attack on Israel's Kerem Shalom crossing killed three Israeli soldiers and wounded several others, three of whom were critically wounded, a spokesperson for the Israel Defense Forces said Sunday. The attack prompted officials to close the terminal, disrupting critical shipments of food and other humanitarian aid into Gaza.

The IDF had "anticipated" the attack, pre-positioned "protective elements" and sirens were triggered, IDF spokesperson Lt. Col. Peter Lerner said. Israel's military will conduct an internal investigation into how and why the casualties occurred despite these measures, he said.

The Israeli military said 14 rockets and mortars launched from the Rafah area hit Kerem Shalom crossing. Hamas said it had been targeting Israeli soldiers in the area. Israel's Channel 12 TV channel said 10 people were wounded.

The IDF launched counter-strikes on the launch site and other locations in Gaza, Lerner said.

The military said the crossing was immediately closed, halting deliveries of aid from there into hard-hit Gaza. It was unclear how long the closure would remain in effect.

The incident came at a time when Gaza is facing a humanitarian crisis with shortages of food, medicine and other humanitarian items.

The attack threatened to complicate the ongoing cease-fire talks in Egypt, which on Sunday appeared to be on the verge of collapse. Egyptian and Hamas officials have said the deal under discussion calls for an extended pause in fighting in exchange for the release of Israeli hostages held by Hamas. But the sides remain at odds over whether the deal would include an end to the war and a complete withdrawal of Israeli troops from Gaza.

Saturday's cease-fire negotiations ended with no developments, a senior Hamas source close to the Cairo talks told CBS News. The source added that "tomorrow, a new round will begin."

Israel did not send a delegation to the talks, saying it would only do so once Hamas replies to Israel's latest proposal. An adviser to Israel Prime Minister Benjamin Netanyahu told CBS News on Saturday that "the end of the war will come with the end of Hamas in Gaza."

The latest round of Gaza cease-fire talks ended in Cairo after "in-depth and serious discussions," the Hamas militant group said Sunday, reiterating key demands that Israel again rejected. After earlier signs of progress, the outlook appeared to dim as Prime Minister Benjamin Netanyahu vowed to resist international pressure to halt the war.

While claiming that Israel has shown a willingness to make concessions, Netanyahu on Sunday said: "Hamas has still held its extreme positions, first and foremost the withdrawal of our forces from the strip, the conclusion of the war and leaving Hamas intact."

"Israel will not agree to Hamas's demands, which would mean surrender; it will continue fighting until all of its objectives are achieved," he said.

Defense Minister Yoav Gallant claimed Hamas wasn't serious about a deal and warned of "a powerful operation in the very near future in Rafah and other places across all of Gaza " after Hamas attacked Israel's main crossing point for delivering badly needed humanitarian aid, killing three soldiers. Israel's military said it believed Hamas was targeting soldiers massed on the Gaza border in preparation for a possible Rafah invasion. Hamas said it targeted soldiers in the area.

But Israeli media reported that CIA chief William Burns, a main mediator in the talks, would meet with Netanyahu on Monday. An official familiar with the matter told The Associated Press that Burns was traveling to meet the prime minister of Qatar, which along with Egypt has been an intermediary dealing with Hamas. It was not clear whether a subsequent trip to Israel that had been planned would happen. The official spoke on condition of anonymity to discuss the closed-door negotiations.

Israel didn't send a delegation to the latest talks. Egyptian state media reported that the Hamas delegation went for discussions in Qatar, where the group has a political office, and will return to Cairo for further negotiations on Tuesday.

In a statement released shortly after Netanyahu's, Hamas chief Ismail Haniyeh said the group is still keen on reaching a comprehensive cease-fire that ends the Israeli "aggression," Reuters reported. Haniyeh also said the deal must guarantee Israel's withdrawal from Gaza, and achieve "a serious" deal to free Israelis being held hostage in exchange for the release of Palestinian prisoners.

Rafah is the southernmost Gaza city on the border with Egypt where more than half of Gaza's 2.3 million residents now seek shelter from Israeli attacks. Rafah is a key entry point for aid.

Israel launched its war in response to the Hamas cross-border attack on Oct. 7, which killed some 1,200 people and took 250 others hostage. An Israeli air and ground offensive has killed over 34,500 people, according to Palestinian health officials, displaced some 80% of Gaza's population and led to a humanitarian disaster.

Egypt and Qatar have been working with the United States to mediate a cease-fire.

CIA director William Burns traveled to Cairo, Egypt, on Friday for the talks. A source with knowledge of the talks told CBS News on Sunday that Burns left Cairo to Doha, Qatar, to hold an emergency meeting with the Qatari prime minister in a bid to prevent the collapse of the mediation efforts. The same source confirmed that the Hamas delegation also left Cairo for Doha.

The latest cease-fire deal, set to last several weeks, proposed by mediators hinges on a swap for hostages. In the proposed deal, for every one hostage Hamas releases, Israel would have to release a larger number of Palestinians held in Israeli jails. 

On Sunday, Netanyahu's Cabinet approved a measure to shutter Qatar's Al Jazeera news channel, accusing it of broadcasting anti-Israel incitement. The decision threatened to further disrupt the cease-fire talks. There was no immediate comment from Qatar.

In:
• Hamas
• Israel
• Gaza Strip
• Egypt
• Benjamin Neta​nyahu