US President Donald Trump has called the congressional impeachment investigation that may seek to remove him from office "a lynching".

In a tweet Mr Trump condemned the inquiry as "without due process or fairness or any legal rights".

Democrats may seek to impeach the Republican president by Christmas.

A racially loaded term in the US, lynching refers to historic extrajudicial executions by white mobs mainly against African Americans.

White House deputy press secretary Hogan Gidley said: "The president has used many words, all types of language, to talk about the way the media has treated him."

He added: "The president wasn't trying to compare himself to the horrific history in this country at all."