US president Joe Biden tweeted about the Hamas massacre in Israel on Tuesday.

"This is not some distant tragedy – the ties between Israel and the United States run deep," Biden wrote.

"It is personal for so many American families who are feeling the pain of this attack as well as the scars inflicted through millennia of antisemitism and persecution of Jewish people.

"In cities across the country, local and federal law enforcement partners are closely monitoring for any domestic threats in connection with the horrific terrorist attacks in Israel."