Donald Trump can't block people on Twitter, a US appeals court has found.

The president cannot infringe the first amendment rights of citizens by banning them from being able to see his tweets or post messages to him, the court decided.

The constitution does not allow Mr Trump "to exclude persons from an otherwise open online dialogue because they expressed views with which" he disagreed, the judges said.

Mr Trump had admitted to blocking the users because they had criticised him or his policies. But he had argued his account was private and that he could use it to ban whichever uses he wanted.

The president and a number of his staff members had been sued by a host of social media users who had been blocked by him on Twitter, meaning they could no longer see his profile or send tweets to him.

They argued that his Twitter account was a public forum and that they therefore could not be banned from taking part in it by the president.

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Judges in the US Court of Appeals agreed, and banned Mr Trump from blocking them on the site.

The ruling was clear that the court had not considered whether it would be permissible for public officials to ban people on their private accounts. It also gave no consideration to whether or not the first amendment applies to technology and social media companies in the way they police their platforms.

But it did conclude that it was not allowed for a public official who uses a social media account for official purposes to ban people they disagree with.

Mr Trump's lawyers had argued that the account should be allowed to block users because it was run as a private and personal account, and when he was banning them from seeing his tweets he was acting in that capacity. That argument was rejected.

The judges decided that despite the fact Mr Trump established the account before he ran for president, and that it will presumably return to being a personal account after he leaves office, for now it retains "all the trappings of an official, state‐run account".