By Jasper Ward and Kanishka Singh
WASHINGTON (Reuters) -U.S. President Joe Biden said on Monday that at least 11 American citizens were among those killed in Israel following the weekend's attacks by Palestinian Islamist group Hamas.
Washington believes it is likely U.S. citizens are also among those being held hostage by Hamas, Biden said in a statement.
White House national security spokesman John Kirby (NYSE:KEX) later added it was not yet confirmed if Americans were taken hostage.
"I can't say definitively that we know Americans are being held hostage. That said, we have to accept the grim possibility that some are," Kirby told reporters late on Monday.
Biden said the United States was working with Israeli officials to obtain more information as to the whereabouts of U.S. citizens who are still unaccounted for.
"For American citizens who are currently in Israel, the State Department is providing consular assistance as well as updated security alerts," Biden said.
"For those who desire to leave, commercial flights and ground options are still available," he said, adding that they should take precautions and follow the guidance of local authorities.
Hamas launched a surprise attack on Israel on Saturday killing hundreds of Israelis and seizing dozens of hostages. Israeli TV channels said the death toll from the Hamas attack had climbed to 900, with at least 2,600 injured.
Israel subsequently battered Palestinians with air strikes in Gaza. Gaza's Health Ministry said at least 687 Palestinians have been killed and 3,726 wounded in Israeli air strikes on the blockaded enclave since Saturday.
Biden said he has directed his team to work with Israeli counterparts on every aspect of the hostage situation, including sharing intelligence and deploying experts from the U.S. government.
Police departments across the U.S. have stepped up security around centers of Jewish life, Biden said.