US President Donald Trump has condemned dozens of violent threats made against US Jewish community centres in the past few 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 anti-Semitic threats targeting our Jewish community and community centres are horrible and painful", he said.
The FBI opened an investigation on Monday following more threats.
"I will tell you that anti-Semitism is horrible and it's going to stop and it has to stop," Mr Trump said in an interview with NBC earlier on Tuesday.
Last week, 27 Jewish community centres in at least 17 US states reported receiving hoax bomb threats. On Monday 11 more were made across the country.
No bombs were found at any locations, and normal services resumed following building evacuations.