It doesn't take much to provoke US President Donald Trump into blocking a follower on Twitter - anything from an insult to an unflattering gif to a mild "covfefe" joke seems enough to do the trick.

So it perhaps shouldn't come as a surprise that bestselling author Stephen King was abruptly added to the #BlockedByTrump list on Tuesday.

The horror fiction maestro has been one of Trump's most consistent and creative Twitter critics since well before the November election.

"A Trump presidency scares me more than anything else," he told Ron Charles, editor of The Washington Post's Book World, during a Facebook Live interview in September. "I'm terrified that he'll become president."