US President Donald Trump on Tuesday decried anti-Semitic threats against Jewish community centers "horrible" and "painful," promising to work to bridge divisions in the country.

"This tour was a meaningful reminder of why we have to fight bigotry, intolerance and hatred in all of its very ugly forms," Trump said in remarks after visiting the National Museum of African American History and Culture in Washington.

"The anti-Semitic threats targeting our Jewish community and community centers 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."

Nearly a dozen Jewish community centers received bomb threats that prompted evacuations on Monday. At the weekend, more than 100 headstones were damaged at a Jewish cemetery in St Louis, Missouri, the facility's director said