The president, who has spent much of the past two days threatening North Korea and congressional Republicans on Twitter and in other public statements, remained silent on the violence for most of the morning even as House Speaker Paul D. Ryan, Mr. Trump’s wife, Melania, and dozens of other public figures condemned a march by white nationalists chanting anti-Semitic slurs.
Mr. Trump first weighed in at 1:19 p.m. “We ALL must be united & condemn all that hate stands for. There is no place for this kind of violence in America. Lets come together as one!” the president said on Twitter.
Mr. Trump did not single out the marchers, who included the white supremacist Richard Spencer and the former Ku Klux Klan leader David Duke, for their ideology. He did, however, amend his original tweet to include a reference to Charlottesville.
His response drew criticism from Democrats. “Until @POTUS specifically condemns alt-right action in Charlottesville, he hasn’t done his job,” Senator Chuck Schumer of New York, the Democratic leader, said in a tweet posted after Mr. Trump’s Twitter messages.
More than a half-hour before the president commented, Melania Trump, using her official “@FLOTUS” Twitter account, wrote, “Our country encourages freedom of speech, but let’s communicate w/o hate in our hearts. No good comes from violence. #Charlottesville.”
Mr. Ryan was even more explicit. “The views fueling the spectacle in Charlottesville are repugnant. Let it only serve to unite Americans against this kind of vile bigotry,” he wrote on Twitter at noon, around the time that Gov. Terry McAuliffe of Virginia declared a state of emergency in the typically sleepy college town.
The president has long denied any connection or affinity to so-called alt-right, racist or anti-Jewish groups, although some of his supporters have made little secret of their beliefs.
On Friday night, hundreds of alt-right demonstrators, some wearing red hoods, some waving Confederate flags, many brandishing lit lawn torches, marched on the picturesque grounds of the University of Virginia. The marchers included Mr. Spencer and Mr. Duke.
Alt-right refers to a far-right fringe movement that embraces white nationalism and a range of racist and anti-immigrant positions.
“We’re going to fulfill the promises of Donald Trump” to “take our country back,” Mr. Duke told reporters on Saturday. Other members of the group carried “Trump” campaign placards.
The president has at other times been tough on protesters, especially when so-called resist groups took to the streets in several cities early in his presidency. “Professional anarchists, thugs and paid protesters are proving the point of the millions of people who voted to MAKE AMERICA GREAT AGAIN!” Mr. Trump wrote on Twitter in February.
Mr. Trump has also drawn criticism for his muted reaction to the bombing of a mosque in Bloomington, Minn., on Aug. 5. Mark Dayton, the state’s Democratic governor, called the attack “an act of terrorism,” and Senator Al Franken, also a Democrat, called the bombing “an attack on all of us.”