ABOUT 100 headstones at a Jewish cemetery in Philadelphia have been knocked over, police said on Sunday, in the latest apparent vandalism incident at a Jewish burial ground in the United States.

A Mount Carmel Cemetery visitor called police on Sunday morning to say the gravestones of three of his relatives had been toppled, police said in a statement. Officers found about 100 others knocked down. The incident apparently took place after dark on Saturday, police said.

ABC television affiliate WPVI said the damage was widespread and footage showed rows of headstones knocked down.

"I'm hoping it was maybe just some drunk kids. But the fact that there's so many, it leads one to think it could have been targeted," cemetery visitor Andrew Mallin, who had come to see his father's grave, told the station.

The Anti-Defamation League, a watchdog group that monitors hate groups, is offering a $10,000 reward in the case, supported by the Mizel Family Foundation, police said.

Israeli Foreign Ministry spokesman Emmanuel Nahshon said on Twitter: "#Philadelphia Jewish cemetery desecration is shocking and a source of worry. Full confidence #US authorities catch and punish culprits."

The apparent vandalism came about a week after about 170 headstones were damaged at a Jewish cemetery in St. Louis. Jewish community centers across the United States have also

reported a surge in bomb threats, but all were hoaxes.

Muslim Americans have helped raise about $131,000 to repair the St. Louis cemetery, far exceeding organizers' $20,000 goal, according to their LaunchGood website.

Some Jewish groups have described the vandalism and threats as the latest evidence that Donald Trump's election as U.S. president had emboldened anti-Semitic groups. His campaign last year drew the support of white nationalists and right-wing groups, despite his disavowals of them.

Trump delivered his first public condemnation of anti-Semitic incidents on Tuesday. The threats are "horrible and are painful and a very sad reminder of the work that still must be done to root out hate and prejudice and evil," he said.

Some Jewish organizations have criticized his approach. The Anne Frank Center for Mutual Respect in New York called his comments "a Band-Aid on the cancer of anti-Semitism that has infected his own administration."

Jewish groups had also criticized the White House for omitting any mention of Jews in its statement marking Holocaust Memorial Day last month.