Declaring himself “the president of law and order,” President Donald Trump on Monday announced he is considering measures to put down the “riots and lawlessness” that have gripped the nation since the death of George Floyd.

“My first duty is to defend our great country,” Trump said in a six-minute speech in the Rose Garden. “All Americans were rightly sickened and revolted by the death of George Floyd. I will fight to keep them safe,” he said.

The president threatened to invoke the Insurrection Act of 1807, a federal law that allows the president to deploy military troops within the United States to suppress civil disorder, insurrection and rebellion.

If he deems it necessary, the president said he would mobilize “thousands” of U.S. troops along with the National Guard to “dominate the streets” until the violence has been quelled. He said he would send military forces into states even if they do not give explicit consent for him to do so, if the need arises.

“My administration is fully committed that for George and his family, justice will be served,” Trump said. “He will not have died in vain. But we cannot allow the righteous cries of peaceful protesters to be drowned out by an angry mob.”

Trump blamed “professional anarchists” for the widespread rioting and mayhem, again mentioning the American militant anti-fascist movement Antifa.

He called the previous night’s protests in front of the White House “a total disgrace.”

During a Friday night protest, the first family had to be moved to a bunker for about an hour as the situation escalated.

Earlier Monday, Attorney General William Barr stood across the street from the White House in Lafayette Park, surveying thousands of protesters gathered peacefully, but still being  fenced off by Secret Service and military police.

Nine large military trucks carrying troops with helmets on were parked outside the White House, according to reports.

Moments after Trump declared himself “an ally of all peaceful protesters,” a wild scene erupted as troops and authorities launched tear gas, rubber bullets and flash bangs to disperse the protesters gathered peacefully outside the White House.

Explosions could be heard from the Rose Garden about an hour before a city curfew went into effect, according to reports.

In a surprise move, after the crowds were cleared, Trump emerged from the White House gates and walked a block to St. John’s Episcopal Church, which had been damaged in more fierce protests the previous night.

The president was escorted to the site by dozens of armed Secret Service agents.

In front of the historic church entrance, the president stood for photographs with a Bible raised in his right hand, saying he wanted to honor the establishment on the day after protesters set a small fire inside the building, which is more than 200 years old.

Episcopal leaders later expressed outrage over Trump’s visit, saying he used “one of our churches as a prop.”

Earlier Monday

After telling the nation’s governors that Washington, D.C., was under control during Sunday night’s violent protests and fires, Trump derided many governors as “weak” and demanded tougher crackdowns on burning and stealing among some demonstrations in the aftermath of another night of violent protests in dozens of American cities.

Earlier in the day, Trump spoke to governors on a video teleconference that also included law enforcement. The president said governors “have to get much tougher” to end the uprisings.

“Most of you are weak,” Trump said. “You’ve got to arrest people, you have to track people, you have to put them in jail for 10 years and you’ll never see this stuff again. We’re doing it in Washington, D.C. We’re going to do something that people haven’t seen before.”

Washington was the site of several fires and violent protests Sunday night as the nation continues to reel with the racial and social aftershocks in the death of an unarmed black suspect in Minneapolis police custody.

The president urged the governors to deploy the National Guard, which he credited for helping calm the situation Sunday night in Minneapolis. He demanded that similarly tough measures be taken in cities that also experienced a spasm of violence, including New York, Philadelphia and Los Angeles.

The president told the governors they were making themselves “look like fools” for not calling up more of the National Guard as a show of force on city streets.

Barr, who was also on the call, told governors that a joint terrorist task force would be used to track agitators and urged local officials to “dominate” the streets and control, not react to crowds, and urged them to “go after troublemakers.”

Several news and social media reports recounted violence throughout the city, including near the White House.

More than 50 Secret Service agents were injured in Sunday night's violence, according to Fox News.

Trump was taken to an underground White House bunker amid protests Friday due to terroristic threats, according to reports. He was there only for a short time.

Trump is blaming Antifa as one of the sources for the protests that have rocked the nation since the death of Floyd, who died while in Minneapolis police custody over Memorial Day weekend.

Antifa is regarded as a militant, left-wing, anti-fascist political activist movement in the United States.

»MORE: Who was George Floyd?

It is made up of autonomous activist groups that try to achieve their political objectives through direct action instead of policy reform.

Activists from the group reportedly have engaged in various protest tactics including property damage, physical violence and harassment against those whom they identify as fascist, racist or on the far right.

Trump said the U.S. will designate Antifa as a terrorist organization.

Trump did not appear in public Sunday.

In recent days, security at the White House has been reinforced by the National Guard and additional personnel from the Secret Service and the U.S. Park Police.

Clarification: A previous version of this story said President Trump had invoked the Insurrection Act. At his news conference Monday, Trump threatened to invoke the act. The Atlanta Journal-Constitution regrets the error.