Twitter escalated its confrontation with President Donald Trump on Friday, adding warning labels to two tweets by Trump and the official White House Twitter account that implied that protesters in Minneapolis could be shot.

Amid the unrest in Minnesota, Trump posted a message on Twitter early Friday saying that “when the looting starts, the shooting starts.” Twitter quickly prevented users from viewing the tweet without reading a brief notice that the post glorified violence, the first time it had applied such a warning on any public figure’s tweets. The official White House account then reposted Trump’s message; Twitter responded by adding the same notice.

Twitter’s actions came a day after Trump signed an executive order to limit its legal protections under a statute that shields social media companies from liability for the content posted on their platforms. Twitter publicly opposed the executive order, calling it “a reactionary and politicized approach to a landmark law,” ramping up a conflict with Trump that has exploded this week.

The decision to add the new warning labels was approved by Jack Dorsey, Twitter’s chief executive, after a late-night debate among company officials, said a person with knowledge of the deliberations. Twitter further tightened restrictions on the messages from Trump and the White House by blocking users from liking or replying to them, though people could still retweet the messages if they added a comment of their own.

But Twitter did not go as far as taking the posts down, saying it was in the public’s interest that the messages remain accessible.

The back-and-forth between Trump and Twitter on Friday punctuated a week of conflict between the two.

The tussle began after Trump tweeted a hurtful and unsubstantiated conspiracy theory this month to attack MSNBC host Joe Scarborough, which caused critics to call on Twitter to remove the messages. While Twitter did not take those posts down, it added fact-checking labels for the first time to two of the president’s election-related posts Tuesday. The labels stood out because Twitter for years did little to moderate Trump’s often inaccurate and threatening posts.

That immediately ignited Trump’s ire. He accused Twitter of stifling free speech and said he would not allow the social media companies to operate unfettered. And in an apparent act of retaliation, he signed the executive order Thursday taking aim at Section 230 of the Communications Decency Act, which provides the liability shield to the tech companies.

Twitter and Trump are now in a standoff. The company has said it will continue putting warning labels and restrictions on tweets that incite violence or spread false information about elections and the coronavirus. And Trump, who once tweeted up to 108 times a day this month, shows no signs of stopping his usage of the service, lashing out Friday on Twitter about Twitter itself.

“Twitter is doing nothing about all of the lies & propaganda being put out by China or the Radical Left Democrat Party,” he wrote. “They have targeted Republicans, Conservatives & the President of the United States. Section 230 should be revoked by Congress. Until then, it will be regulated!”

He posted several other tweets citing similar views by his favorite Fox News hosts. And as if daring Twitter, he posted another message about looting leading to shooting Friday afternoon.

In its separate Twitter account, the White House jabbed directly at Dorsey: “The President did not glorify violence. He clearly condemned it. @Jack and Twitter’s biased, bad-faith ‘fact-checkers’ have made it clear: Twitter is a publisher, not a platform.”

And Dan Scavino, the president’s deputy chief of staff, said Twitter should be targeting the protesters in Minneapolis.

“Twitter is targeting the President of the United States 24/7, while turning their heads to protest organizers who are planning, plotting, and communicating their next moves daily on this very platform,” he wrote. He added that Twitter was full of it and “more and more people are beginning to get it.”

Twitter said it had decided to restrict Trump’s tweet about the protests in Minnesota “based on the historical context of the last line, its connection to violence, and the risk it could inspire similar actions today.” It had applied a warning label on a tweet from the Brazilian minister of citizenship, Osmar Terra, last month, but the label was not for glorifying violence.

Dorsey also tweeted Friday morning that social networks’ fact-checking process should use open-source technology — software that is created and shared for general use — and be verifiable by everyone. He did not respond to a request for comment.

The conflict has thrown Twitter into chaos, with employees racing to take action on Trump’s tweets while also scrambling to protect themselves from harassment. After Trump and his allies lashed out at one Twitter employee who had publicly criticized Trump and other Republican leaders, other employees removed their company affiliation from their social media profiles or locked their accounts from public view.

First Amendment scholars said Friday that Trump and his allies had it backward and that he was the one trying to stifle speech that clashed with his own views.

“Fundamentally this dispute is about whether Twitter has the right to disagree with, criticize and respond to the president,” said Jameel Jaffer, executive director at the Knight First Amendment Institute at Columbia University. “Obviously, it does. It is remarkable and truly chilling that the president and his advisers seem to believe otherwise.”

Revoking Section 230 protections would expose Twitter and other online platforms to expansive potential legal vulnerability that could undermine the fundamentals of their businesses. But it would also remove the very legal standard that has allowed Trump to use Twitter so effectively to communicate with his more than 80 million followers — no matter how incendiary, false and even defamatory his messages may be.

Without a liability shield, Twitter and online companies would be forced to police accounts like Trump’s even more closely to guard themselves against legal action.

Twitter has for years faced criticism over Trump’s posts on the platform. The company has said repeatedly that the president did not violate its terms of service, however much he appeared to skirt the line. It has also said that blocking world leaders from the service or removing their tweets would hinder public debate.

Twitter did announce last year, however, that it would in certain cases place warning labels on posts from political figures that broke its rules, the feature it used with Trump’s tweet about Minneapolis.

Trump’s message implying that the Minneapolis protesters could be shot was also posted on his official Facebook page, where it appears without any warning labels. Mark Zuckerberg, the company’s chief executive, told Fox News this week that he was uncomfortable with Facebook’s being “the arbiter of truth of everything that people say online.”

Protests have raged in Minneapolis this week over the death Monday of George Floyd, a black man who had been pinned down by a white police officer who pressed his knee on Floyd’s neck.

Frederike Kaltheuner, a tech policy fellow at the Mozilla Foundation, said Twitter’s confrontation with Trump raised questions about how the platform would treat other world leaders. In March, the company deleted posts by the presidents of Brazil and Venezuela that contained unproven information about COVID-19 treatments.

“I doubt that Twitter has the resources to consistently apply rules to all heads of states that use their platform in all sorts of languages,” Kaltheuner said. “From all we know about the many inconsistent ways in which other policies are being enforced, my guess is that places that rarely make U.S. news will likely be overlooked.”

In Trump’s tweets about Minneapolis on Friday, he also criticized the response by Mayor Jacob Frey, a Democrat. Trump said Frey must “get his act together and bring the City under control, or I will send in the National Guard & get the job done right.”

Frey did not know about Trump’s tweets until a reporter read them aloud during a news conference early Friday. The mayor shook his head and slammed a podium for emphasis.

“Weakness is refusing to take responsibility for your own actions,” he said. “Weakness is pointing your finger at somebody else during a time of crisis.”

He added, “Donald Trump knows nothing about the strength of Minneapolis.”