The White House believes Israel is "making an effort" to minimize civilian deaths in Gaza, a senior official said Sunday, as international concern mounted over the numbers killed in the resumed war with Hamas.

Speaking on the US Sunday talk shows, National Security Council spokesman John Kirby also insisted that US intelligence was unaware of any secret, advanced Hamas blueprint for its brutal 7 October attack on Israel that triggered the conflict.

The New York Times reported last week that Israeli authorities had obtained such a document a year before the attack occurred.

According to Hamas, more than 15,500 people have been killed in Gaza since the beginning of the war, but Kirby told ABC's "This Week" that Israel had responded to US appeals to protect civilians.

"We believe they have been receptive to our messages here of trying to minimalize civilian casualties," he said, including by publishing online a map of places where Gazans could go to find safety. 

"There's not a whole lot of modern militaries that would do that… to telegraph their punches in that way. So they are making an effort."

His comments came as Israel has resumed its intensive air and ground campaign following a week-long truce. 

Ron Dermer, Israel's minister of strategic affairs, insisted on ABC that efforts to minimize civilian casualties were deliberate and "unprecedented." 

"If we wanted to do it fast," he said, "we'd harm a lot more civilians."

International concern has been intensifying over the toll in Gaza.

"I cannot find words strong enough to express our concern over what we're witnessing," the head of the World Health Organization, Tedros Adhanom Ghebreyesus, said Sunday on X, formerly Twitter, demanding a "Ceasefire. NOW."

Kirby was also asked about the New York Times report on the Hamas attack plan, which the newspaper said Israeli officials had dismissed as beyond the militant group's ability to carry out.

"Our intelligence community is taking a look into that," Kirby said while adding that there were "no indications that we, the United States intelligence community, had any knowledge of that document beforehand or any visibility into it."

The unprecedented 7 October assault on southern Israel killed 1,200 people, most of them civilians, according to Israeli authorities.