Twitter has hidden a tweet from US President Donald Trump in which he threatened to use "serious force" against protesters in Washington, saying it broke rules over abusive content.
The move appeared to be the first by Twitter against the president for an "abusive" tweet. In a growing dispute, the platform has recently labeled other tweets by Mr Trump as misleading and violating its standards on promoting violence.
"There will never be an 'Autonomous Zone' in Washington, DC, as long as I'm your President. If they try they will be met with serious force!" Mr Trump tweeted.
The action by Twitter requires users to click through to read the tweet, with a tag on the message that it "violated the Twitter rules about abusive behavior" but that it would remain accessible "in the public's interest."
Mr Trump's tweet referred to the police-free district created by protesters in Seattle, in Washington state, two weeks ago, which has sparked outrage among conservatives.
Twitter's move escalated the battle between the White House and social media firms which Mr Trump has accused of bias against conservatives, despite his own large following.
The president has already signed an executive order which could lead to more government oversight of social media firms, despite doubts about its legal authority.
The Trump administration has also signalled it wants to overhaul a law that gives online services immunity from content posted by others, a move which could open the floodgates to litigation.
Twitter said in a statement to AFP it took the action because the tweet violated its policy against abusive behavior with "a threat of harm against an identifiable group."
Twitter's policy in dealing with world leaders in most cases calls for violating messages to be labeled - which limits its reach and prevents others from liking or retweeting it - but leaves the tweets available because if they relate to "ongoing matters of public importance."
The new, aggressive stand by Twitter on rule-breaking by the president stands in contrast with Facebook, which has maintained a largely hands-off policy despite pressure from activists to curb inflammatory content.
Facebook did remove a Trump ad last week that contained a symbol used in Nazi Germany for political prisoners, saying it violated the platform's policy against "organised hate."