US President Joe Biden and Democratic presidential candidate Kamala Harris mourned the bloody Hamas attack on Israel a year ago Monday while deploring heavy civilian losses of Palestinians in the subsequent Israeli operation.

"Let us bear witness to the unspeakable brutality of the October 7th attacks but also to the beauty of the lives that were stolen that day," Biden said.

Harris, the vice president, said she would "never forget the horror of October 7, 2023" when Hamas militants launched a surprise attack into Israel, killing 1,205 people, most of them civilians, and taking 251 hostages.

"I am devastated by the loss and pain of the Israeli people," she said in a statement.

But Biden added in his statement "that history will also remember October 7 as a dark day for the Palestinian people because of the conflict that Hamas unleashed that day."

"Far too many civilians have suffered far too much during this year of conflict," he said.

In her statement, Harris also described herself as "heartbroken over the scale of death and destruction in Gaza over the past year."

More than 41,909 Palestinians, a majority of them civilians, have been killed in Israel's military campaign in the Gaza Strip since the war began, according to data provided by the health ministry in Hamas-run Gaza. The UN has acknowledged these figures as reliable.

In their statements, Biden and Harris both underlined their commitment to the US military alliance with Israel.

"One year later, Vice President Harris and I remain fully committed to the safety of the Jewish people, the security of Israel, and its right to exist," Biden said.

Harris noted that she would "always fight for the Palestinian people to be able to realize their right to dignity, freedom, security, and self-determination."

"We also continue to believe that a diplomatic solution across the Israel-Lebanon border region is the only path to restore lasting calm," she said, referring to the escalating war between Israel and Hezbollah in Lebanon.