Biden bemoans 'appalling surge' in anti-Semitism amid Gaza war

US President Joe Biden on Sunday marked six years since a deadly synagogue attack in Pittsburgh by lamenting an "appalling surge" of anti-Semitism since the war in Gaza started.

In 2018, a rightwing extremist killed 11 Jewish worshippers at a synagogue in the former Pennsylvania steel hub in America's deadliest anti-Semitic attack.

This year's commemoration falls on the Hebrew calendar anniversary of the Hamas attack on October 7 last year that sparked the war in Gaza.

"One year later, the trauma and losses from that day and its aftermath are not only raw, but exacerbated by the appalling surge of anti-Semitism against Jews in America and around the world," said Biden in a statement.

Biden, whose administration has backed Israel since the start of the conflict, said he had launched before October 7 the country's first National Strategy to Counter Antisemitism.

"We are aggressively implementing it," he said, adding that his administration had secured $1.2 billion to provide physical security of synagogues, Jewish schools and other non-profit organisations.