(Bloomberg) -- The Israel Defense Forces increased strikes on Hamas targets in the southern Gaza Strip on Saturday, a day after US Secretary of State Antony Blinken urged Israel to do all it can to protect civilian lives.

The switch in focus toward the densely-populated south followed the end of a week-long truce between Israel and Hamas. Talks have resumed in Qatar to discuss a new cease-fire, Reuters reported.

Israel’s strikes on Saturday were focused on the Khan Younis area in southern Gaza, where the military said it had struck more than 50 Hamas targets with airstrikes, tank fire and its navy.

Blinken’s message to Israeli Prime Minister Benjamin Netanyahu has grown more stern on each of his three visits to the region since Hamas, which is designated a terrorist organization by the US and European Union,, attacked Israel on Oct. 7.

Aides bristled during Blinken’s first trip at any suggestion that Israel heed humanitarian concerns as it prepared an initial response to the Hamas attacks. The second time around, Blinken stressed that that Israel’s conduct of the war mattered.

By this week, as estimates of Palestinian deaths in Gaza since Oct. 7 climb above 15,200, according to the Hamas-run health ministry, Blinken gave a direct warning to Israel’s war cabinet — that the devastation unleashed on northern Gaza must not be repeated. More than 70% of those killed in the recent Gaza attacks are said to be women and children.

That shift in tone underscored a growing sense of alarm among senior Biden administration officials about what fresh crisis awaits now that the Gaza war has resumed and Israel turns its military attention to Gaza’s south. Hundreds of thousands of civilians have fled there in Israel’s orders — and now have nowhere else to flee.

Publicly, Israel remained defiant. Hours after Blinken left, the Hamas-run border crossing authority said no aid had been delivered since the truce had ended early Friday. The evacuation of wounded people and dual nationals to Egypt, and the return of Gazans stranded in Egypt, also stopped.

Aid resumed on Saturday, the Palestinian Red Crescent said in a post on X, formerly Twitter.

Gaza authorities also reported that some 100 people had been killed in a fresh round of Israeli airstrikes. Another 100 or more were killed in the bombing of a house in the Jabalia camp in the northern Gaza Strip that had been used as shelter for families and displaced persons, according to Palestinian TV.

Blinken’s evolving message has reflected President Joe Biden’s own change in stance as his administration responds to pressure from Arab allies, human-rights activists and Americans back home — especially the left flank of his own party — who believe the civilian death toll is too high.

“I made clear that after the pause it was imperative that Israel put in place clear protections for civilians and for sustaining humanitarian assistance going forward,” Blinken said in Dubai, moments before boarding a plane back to Washington.

Whether it makes a difference is an open question. A senior US official, who asked not to be identified discussing private deliberations, said Israel genuinely seems to be trying to meet US demands on creating civilian safe zones, and heard Blinken’s insistence that results on the ground — like fewer civilian casualties — are more important than intent.

In what may be an attempt to protect civilians, the Israel Defense Force has begun using a micro-zone map in Gaza to issue alerts to residents in certain areas, urging them to evacuate immediately.

Read More: White House Says Israel ‘Mindful’ of Need to Protect Civilians

Netanyahu, who warned during the week-long pause that Israel’s campaign wasn’t over, was similarly unsparing in his description of the nation’s goals. The senior US official said Blinken asked the Israelis how much longer they expected the campaign to last, and didn’t get a clear answer.

“Our forces are charging forward,” Netanyahu said on Friday. “We continue to fight with all our might until we achieve all our objectives — the return of all our hostages, the elimination of Hamas, and ensuring that Gaza will never again pose a threat to Israel.”

Those concerns masked what otherwise has been a success: under intense pressure from the US and with mediation by Qatar, Israel and Hamas managed seven days of a truce in which dozens of Israeli hostages captured in the Hamas attack had been freed, along with many more Palestinian prisoners held in Israel.

Read more: The West Bank Is Being Reshaped Along With Gaza Post-Oct. 7

Israel had also allowed more and more humanitarian aid to flow, and US officials had impressed upon Netanyahu to take their concerns into account. Blinken said the US was still focused on making sure the conflict doesn’t spread in the region — so far, a successful effort — and looking toward what he called a “just, lasting and secure peace” for the Palestinian territories.

Yet as the truce collapsed, Israel and the US saying Hamas had carried out a deadly attack and reneged on commitments to release more women hostages. Hamas said Israel was to blame - a familiar cycle of finger-pointing.

Blinken told reporters that Hamas had fired rockets at Israel while the cease-fire was still in effect, and, separately, killed Israelis at a bus stop.

Earlier: Hamas Popularity in West Bank Stalls Israeli Bid to Crush It

“Clearly the first phase of the operation, before the cease-fire, exacted such an enormous cost,” said Brian Katulis, vice president of policy at the Middle East Institute in Washington. “A lot of those people were told to move south. Now the campaign’s moving south. And that’s the real worry that a lot of people in the administration have.”

Defense Secretary Lloyd Austin, speaking to reporters in California on Friday, said that each time he speaks to his Israeli counterpart, Yoav Gallant, “I remind him of the necessity to make sure that we’re protecting innocent civilians and creating pathways for civilians to move out of out of the battle space.”

Outside experts said the idea of creating civilian safe zones and doing more to avoid a humanitarian catastrophe wouldn’t be easy for Israel, given that doing so would likely put more of its soldiers in harm’s way.

For Israeli, “if they’re going to firm up the rules of engagement to reduce these civilian casualties, the implication there, which is absolutely direct, is that they will have to take more on-the-ground military casualties,” Frank Ledwidge, former military intelligence officer and lecturer in strategy at Portsmouth University in the UK, told Bloomberg Radio. “Let’s see if they have the appetite for that.”

--With assistance from Iain Marlow and Peter Martin.

(Recasts with new strikes, aid delivery from third paragraph.)

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Author: Courtney McBride