At least three Americans have been killed in the surprise Hamas terror attack on Israel near the Gaza border, officials said Sunday.

Several other US citizens are still unaccounted for, according to an internal US government memo obtained by CNN.

The identities of the three dead Americans have yet to be made public.

Secretary of State Antony Blinken revealed earlier Sunday that his office was working to verify the number of Americans killed and missing in Israel after Hamas coordinated several attacks at the border site.

“Yes, we have reports that several Americans were killed. We’re working overtime to verify that,” Blinken told CNN’s “State of the Union.” 

“At the same time, there are reports of missing Americans and there again, We’re working to verify those reports,” he added without providing an estimate.

The US Embassy in Jerusalem had put out an order for Americans to “shelter in place” during Saturday’s assault, with the office updating its contingency plans “for any potential evacuation by land or air.”

More than 700 Israelis were killed and over 2,000 wounded in the “war,” with the Israeli Prime Minister’s office adding that more than 100 people have been taken hostage by the terrorist group.

Israel has since officially declared war and launched retaliatory attacks on Palestine, which has also seen civilian casualties as a result.

About 370 Palestinians have been killed, with another 1,990 reported missing, according to the Palestinian Health Ministry.

Blinken said America will stand behind its ally Israel to defend itself against Hamas, with Defense Secretary Lloyd Austin also announcing Sunday that the US will provide additional equipment and resources to the Israel Defence Forces.