The Israeli military has killed at least 18 people in multiple strikes across Gaza after Prime Minister Benjamin Netanyahu ordered the military to resume its assault on the war-devastated enclave, claiming that Hamas violated the United States-brokered ceasefire.

Hospital sources told Al Jazeera on Tuesday that four Palestinians were killed in the Sabra neighbourhood of Gaza City and five in Khan Younis. At least 50 were injured across the territory, as the truce now faces its most serious test.

Earlier, Netanyahu’s office said in a statement that he had instructed the military to “immediately carry out powerful strikes” after “security consultations”.

Reporting from Gaza City, Al Jazeera’s Hani Mahmoud said a missile had fallen behind the al-Shifa Hospital and that there had been “major activity in the air over Gaza’s skies, with drones hovering above”.

“Eyewitnesses described the strike as massive. We are in an area about 20 minutes away, and we could hear it from here,” he said. “The attack caused a state of mayhem and panic among patients and medical staff inside the hospital.”

US Vice President JD Vance said the ceasefire was holding despite the Israeli strikes in Gaza City amid accusations from both sides of violations.

“The ceasefire is holding. That doesn’t mean that there aren’t going to be little skirmishes here and there,” Vance told reporters.

“We know that Hamas or somebody else within Gaza attacked an [Israeli military] soldier. We expect the Israelis are going to respond, but I think the president’s peace is going to hold despite that.”

Israel notified the US before its latest deadly strikes in Gaza, The Associated Press news agency reported, citing two unnamed US officials.

Israel’s defence minister, Israel Katz, claimed on Tuesday that Hamas targeted its troops, pledging the group would “pay a heavy price” for alleged attacks on soldiers and for “violating the agreement to return the bodies of the hostages”.

Earlier, Netanyahu had said Hamas had committed a “clear violation” of the ceasefire agreement in Gaza by returning remains belonging to a previously recovered captive.

“Israel must realise that we are committed to the agreement, and they must stop falsely accusing us of violating it,” said Suhail al-Hindi, a member of Hamas’s political bureau in Gaza. He told Al Jazeera the group faced “significant difficulties” during the recovery of the bodies of the Israeli captives.

“We have made every effort possible to recover the bodies, and the occupation bears full responsibility for any delay in recovering the remaining bodies,” he said.

Hamas also rejected any connection to what Israel describes as a shooting attack in Rafah in southern Gaza, which it used to justify the series of deadly air strikes.

The continuing bombing in Gaza “represents a flagrant violation of the ceasefire agreement signed in Sharm el-Sheikh under the auspices of US President Trump”, a Hamas statement on Telegram said.

It called the attack “an extension of a series of violations committed over the past few days, including attacks that resulted in deaths and injuries, and the continued closure of the Rafah crossing, which confirms the insistence on violating the terms of the agreement and attempting to sabotage it”.

There were reports of gunfire in Rafah near the border with Egypt later on Tuesday. It is thought that there was an exchange of fire between Israeli soldiers and Palestinian fighters from the Gaza Strip.

Then, artillery shelling started, and explosions were heard in Rafah and the eastern part of Khan Younis city. There were also reports that one Israeli soldier was injured.

Hamas, the Palestinian Authority and several key Arab and Muslim nations, who added their considerable diplomatic weight to the deal, have accused Israel of multiple violations of the agreement over the last nearly three weeks. Dozens have been killed in Gaza, and Israel is continuing to heavily restrict the flow of aid to those who desperately need it.

Hamas’s military wing announced that it will now postpone the handover of the Israeli captive’s body that it found earlier “due to violations” by Israel.

In a statement, the Qassam Brigades stressed that any Israeli escalation “will hinder search, digging, and retrieval operations of the bodies, which will lead to a delay in recovering the bodies” of the dead captives. They later said they had recovered the bodies of two more dead Israeli captives, Amiram Cooper and Sahar Baruch, during search operations conducted Tuesday.

The latest developments have threatened an already-straining ceasefire agreement and sparked fears of a return to war on Gaza’s bombarded and besieged population.

The latest remains handed over by Hamas earlier were not from the 13 dead captives yet to be returned, according to Netanyahu. Instead, he said they were those of a captive whose body had already been retrieved by Israeli forces nearly two years ago.

A US official told Al Jazeera that locating the bodies of Israeli captives was “difficult, challenging, and time-consuming”. The Civil-Military Co-operation Centre, a US-led body set up to facilitate reconstruction and aid delivery, had played a vital role in bringing Egyptian technical teams into Gaza to retrieve the bodies, said the official.

Netanyahu’s far-right cabinet had called for harsh measures in response, with Finance Minister Bezalel Smotrich urging the re-arrest of Palestinians released in exchanges “in response to Hamas’s repeated and ongoing violations”.

National Security Minister Itamar Ben-Gvir said the correct response was to “destroy [Hamas] completely”.

Other options include halting the already severely limited flow of humanitarian aid to Gaza, expanding Israeli control of the enclave, or ordering air strikes targeting Hamas leaders, according to Israeli media.

Ceasefire hangs in the balance

Since the beginning of the current truce between Israel and Hamas, Netanyahu has been carrying out provocative acts meant to strain the agreement, an analyst says.

“Netanyahu, from the very start of the ceasefire, has been trying to find any trick possible to resume the genocide in Gaza,” Muhammad Shehada, an analyst with the European Council on Foreign Relations based in Copenhagen, told Al Jazeera.

“We see this with Israel refusing to open up the Rafah border crossing, with restricting, until this moment, the amount of aid going in … continuing these bombardments here and there despite the ceasefire being in place under bogus and unsubstantiated claims.”

Shehada said Israel’s leadership is testing the waters to see how far it can go in breaking the ceasefire with Hamas that was orchestrated by US President Donald Trump.

“We see the same thing again and again and again. It’s basically Netanyahu testing the boundaries with Trump and trying to build up a case for resuming the genocide in Gaza,” he added.

But Israeli political analyst Ori Goldberg told Al Jazeera earlier that he thought the dispute was unlikely to derail the entire ceasefire agreement, with the US and its regional partners so heavily invested in the deal to end the two-year war.

“This whole notion that the future, the present of the ceasefire, the assistance millions need so urgently, the chance to end a two-year genocidal campaign — that all of this will simply be thrown out because of a ‘violation’ is ridiculous,” Goldberg said.

Al Jazeera’s Nida Ibrahim, reporting from Doha, Qatar said, “The Israeli prime minister’s hands are tied since the US said it will not allow it to continue its war on Gaza. We know that Americans have more say on what happens and what does not happen in Gaza through the “civil coordination centre” in southern Israel.”

“Now it feels like the Israelis are trying to find these clashes here and there to justify what they always wanted to do – a ceasefire on their own terms in which they can attack who they want and control which borders are open or not,” she added.