US President Donald Trump has condemned bomb threats against US Jewish community centres in recent weeks.
"We have to fight bigotry, intolerance and hatred in all of its very ugly forms," he said while visiting an African-American museum in Washington.
The FBI is investigating the most recent spate of threats on Monday.
Mr Trump was attacked last month when a statement released in his name to commemorate Holocaust Remembrance Day failed to use the word "Jew".
There was also outcry that the statement did not recognise that Jewish people were specifically targeted by Nazi state-sponsored anti-Semitic propaganda.
The president confronted the issue on Tuesday after touring the National Museum of African American History and Culture in the nation's capital.
"The anti-Semitic threats targeting our Jewish community and community centres are horrible and painful," he said.
On Monday 11 Jewish community centres across the country, including in the Houston, Chicago and Milwaukee areas, reported receiving hoax bomb threats.
Last week, 27 Jewish community centres in at least 17 US states received such hoax threats.
No bombs were found at any locations, and normal services resumed following building evacuations.
Police in the state of Missouri have meanwhile opened an investigation after more than 170 headstones were damaged at a Jewish cemetery in St Louis, Missouri, on Monday evening.
In the Canadian city of Toronto, Mayor John Tory has condemned anti-Semitic hate notes left outside the homes of Jewish residents.
Mr Trump's daughter Ivanka - who has converted to Judaism and whose husband is Jewish - also condemned the threats in a tweet on Monday.
She quickly came under fire from social media users pointing out that her father - the president - had not yet condemned the threats.
The US first daughter was also attacked for making no mention of the anti-Jewish nature of the threats.
Hillary Clinton, who lost the election to Donald Trump, on Tuesday morning called upon Mr Trump to address the threats.
In a post on Twitter, she wrote: "JCC threats, cemetery desecration and online attacks are so troubling and they need to be stopped. Everyone must speak out, starting w/@POTUS."
Since the beginning of the year, there have been reports of threats to centres in New York, New Jersey, Ohio, Florida, Massachusetts, Maryland, Michigan, Minnesota, Delaware, Connecticut, Alabama, California, Maine, Tennessee, South Carolina, Missouri, Wisconsin, Texas and Kansas.
The JCC Association of North America, which was targeted in many of the incidents, has since been reviewing its security plans.
"We will not be cowed by threats intended to disrupt people's lives or the vital role Jewish community centres play as gathering places, schools, camps, and fitness and recreation", the JCC said in a statement on Monday.
Since January the JCC has recorded incidents at 69 locations in 27 states and one Canadian province.
The Anne Frank Center for Mutual Respect described Mr Trump's response as "a pathetic asterisk of condescension".
In a scathing Facebook post, spokesman Steven Goldstein said: "When President Trump responds to anti-Semitism proactively and in real time, and without pleas and pressure, that's when we'll be able to say this President has turned a corner.
"This is not that moment."
Mr Trump's condemnation comes after days of criticism that his administration lacked a plan to deal with a recent spike in reports of anti-Jewish threats.
Last week, when he was asked about the matter during a press conference with Israeli Prime Minister Benjamin Netanyahu, Mr Trump cited his presidential election victory.
"I think one of the reasons I won the election is we have a very, very divided nation, very divided. And hopefully, I'll be able to do something about that," he told an Israeli reporter.
Later that week an orthodox Jewish reporter asked Mr Trump about US anti-Semitism, while emphasising that he was not linking the president himself to such incidents.
Mr Trump responded he is the "least anti-Semitic person that you've ever seen in your entire life", before telling the reporter to be quiet as he tried to ask a follow-up question.