Israel’s ambassador to the United States says that Americans have been taken hostage by Hamas militants who swarmed into Israel early Saturday morning in a surprise offensive that caught Israeli security forces off guard.

“I understand there are,” Michael Herzog told CBS News’ “Face the Nation” Sunday morning, “but I don’t have details.”

US Secretary of State Antony Blinken told “Face the Nation” that those reports have not been verified, and that there have also been reports of Americans killed in the offensive.

“We’ve got reports that several Americans are among the dead,” Blinken said. “We’re working very actively to verify those reports. At the same time, the reports of Americans being taken hostage — there too, we’re working to get the facts to find out if those reports are accurate.”

Blinken made the rounds of Sunday morning talk shows and said broadly the same thing to all of them. To NBC News’ “Meet the Press,” he acknowledged that if those reports of American hostages are confirmed, “that is going to be a priority for this government, for this administration, and for me.”

“But I don’t want to get ahead of where we are,” he said. “We have reports; we need to verify them.”

Israeli officials say dozens of Israelis and others have been taken back to Gaza as hostages. They also say 600 Israeli civilians and members of the military have been killed so far as Hamas fired thousand of rockets and infiltrated the heavily guarded border between Gaza and Israel, CBS News reported.

Palestinian officials say more than 300 Palestinians have been killed in retaliatory strikes.

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[Featured image: The flag of Israel is projected onto the front of 10 Downing Street in London to show solidarity with Israel after Hamas launched its unprecedented incursion out of Gaza.  (AP Photo/(Kirsty Wigglesworth)]