US President Joe Biden has announced that at least 11 Americans, "many of whom made a second home in Israel", have been killed in the ongoing conflict between the Hamas militant group and the Jewish nation.

"As we continue to account for the horrors of the appalling terrorist assault against Israel this weekend and the hundreds of innocent civilians who were murdered, we are seeing the immense scale and reach of this tragedy. Sadly, we now know that at least 11 American citizens were among those killed -- many of whom made a second home in Israel," the President was quoted as saying in a statement released by the White House on Monday.

Biden also acknowledged that there were American citizens who still remain unaccounted for.

"We are working with Israeli officials to obtain more information as to their whereabouts."

He went on to say that "the safety of American citizens -- whether at home or abroad -- is my top priority as President".

"While we are still working to confirm, we believe it is likely that American citizens may be among those being held by Hamas. I have directed my team to work with their Israeli counterparts on every aspect of the hostage crisis, including sharing intelligence and deploying experts from across the US government on hostage recovery efforts," Biden added.

He also said that the State Department is currently providing consular assistance and updated security alerts.

"For those who desire to leave, commercial flights and ground options are still available. Please also take sensible precautions in the days ahead and follow the guidance of local authorities," the President urged.

Biden also informed that security has been heightened at Jewish centres and facilities across the US, while the FBI, Department of Homeland Security and other law enforcement agencies were were closely monitoring for "any domestic threats in connection with the horrific terrorist attacks in Israel".

The statement came a day before the President is scheduled to deliver remarks on the conflict on Tuesday, aaccording to a White House official. 

The address is expected to be around 1 p.m. on Tuesday afternoon (about 10.30 p.m IST).

This will mark the second time Biden will speak on camera about the attacks since Hamas launched its deadly assault on southern Israel on October 7. 

Also on Monday, Biden spoke with the leaders of France, Germany, Italy and the UK.

In a joint statement, the countries expressed “steadfast and united support” for Israel and “unequivocal condemnation” of Hamas and, “its appalling acts of terrorism".