Washington — President Donald Trump called anti-Semitic violence “horrible” and vowed on Tuesday to take steps to counter extremism in comments that followed criticism that the White House had not clearly denounced vandalism and threats targeting Jewish institutions.

Hours before Trump’s remarks, Hillary Clinton called on her former presidential rival to speak out against anti-Semitic acts after more than 170 Jewish graves were found toppled at a cemetery in Missouri.

“The anti-Semitic threats targeting our Jewish community at 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,” Trump said following a visit to the Smithsonian’s National Museum of African American History and Culture.

Trump called the tour a “meaningful reminder of why we have to fight bigotry, intolerance and hatred in all of its very ugly forms.” Earlier, he told NBC News that “anti-Semitism is horrible, and it’s going to stop.”

The remarks by Trump also appear aimed at easing pressure on his administration, which faces claims from opponents that it has failed to distance itself from extremist ideology and has emboldened right-wing groups through its populist, America-first themes.

The tweet from Clinton did not specifically mention the gravesite disturbances in University City, Mo., but noted increasing reports of “troubling” threats against Jewish community centers, cemetery desecrations and online intimidation.

Clinton’s message to Trump came as the president of the World Jewish Congress, Ronald Lauder, also urged U.S. officials to recognize that “anti-Semitism is alive and kicking.”

“American Jews are worried,” Lauder said in a statement. “It is shocking to see that Jewish sites are once again being targeted by criminals.”

On Monday, the Anti-Defamation League reported a wave of bomb threats directed against Jewish community centers in multiple states, the fourth series of such threats since the beginning of the year, it said. The development elicited comments from a White House spokesman and Ivanka Trump, neither of which used the phrase “anti-Semitism” or mentioned Jews.

Ivanka Trump’s tweet: “America is a nation built on the principle of religious tolerance. We must protect our houses of worship & religious centers. #JCC”

“Glad to see this,” the ADL’s chief executive, Jonathan Greenblatt, tweeted of Ivanka Trump’s comment. “All Jews need to urge” the president “to step forward & share a plan. His words carry weight. His actions will speak even louder.”

The exchanges were particularly noteworthy in part because of Trump’s unusual response at a news conference last Wednesday with Israeli Prime Minister Benjamin Netanyahu to a question about the rise in anti-Semitic incidents around the country. Rather than condemning them, Trump responded by talking about his electoral college victory.

Trump has been criticized for refusing to describe the threats toward Jews as “anti-Semitism.” An op-ed at the Forward, the New York-based newspaper written for a Jewish audience, described Trump’s “silence about anti-Semitism” as “deeply disturbing.”

When asked again about the rise in anti-Semitic threats, during another news conference on Thursday, the president responded as if he were being personally accused. Trump said that the question was “very insulting” and that he was “the least anti-Semitic person that you’ve ever seen in your entire life.”

The weekend’s events, coming in the wake of last week’s public exchanges with Trump, served to heat up a long-simmering tension between some leaders of the nation’s Jewish community and the Trump White House.

The perpetrators of the cemetery vandalism and their motives are not yet established. Police in University City, an inner-ring suburb of St. Louis, have launched an investigation. They are reviewing video surveillance at the cemetery, which is operated on a not-for-profit basis by the Chesed Shel Emeth Society, and calling on anyone with information to come forward.

Because of the Sabbath, the cemetery does not operate on Saturday, the director of the Chesed Shel Emeth Society, Anita Feigenbaum, told The Washington Post in a phone interview.

A groundskeeper arrived Monday morning to find gravestones overturned across a wide section of the cemetery, the oldest section, bearing the remains of Jews who died between the late 1800s and the mid-20th century.