US Secretary of State Antony Blinken has said that American nationals are likely to be among the killed and others missing in Hamas’s attack on Israel a day earlier.

“We have reports that several Americans were killed. We’re working overtime to verify that. At the same time, there are reports of missing Americans and there again, we’re working to verify those reports,” Blinken told CNN.

He told ABC that “this is a massive terrorist attack that is gunning down Israeli civilians in their towns, in their homes, and as we’ve seen so graphically, literally dragging people across the border with Gaza.

“So, you can imagine the impact this is having throughout Israel. And the world should be revolted at what it has seen.”

Read: Factcheck: Are the videos of Israeli helicopters being shot down real?

Battles between Israeli forces and Hamas continued for the second day after Hamas infiltrated Israel-occupied territories by land, air and sea, killing around 600 Israelis and taking dozens hostage, Al Jazeera reported.

In retaliation, Israel launched airstrikes on Gaza resulting in the killing of at least 313 people and wounding over 2,000 on Sunday, the health ministry in the Palestinian enclave said.

The US, a close ally and major supplier of arms to Israel, could also announce new military support Sunday following the Hamas attack, he said.

“We’re looking at specific additional requests that the Israelis have made. I think you’re likely to hear more about that later today,” Blinken added.

“President (Joe) Biden’s direction was to make sure that we’re providing Israel everything it needs in this moment to deal with the attacks from Hamas.”

The conflict’s worst escalation in decades has claimed more than 600 lives on the Israeli side, the government press office said, while Gaza officials reported at least 370 deaths, with thousands more wounded on each side.