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

Mr Trump condemned the inquiry in a tweet as “without due process or fairness or any legal rights”.

But Democrats were outraged at the president for invoking such a grim and racist chapter from US history.

Lynching refers to historic extrajudicial executions by white mobs mainly against black people.

White House spokesman Hogan Gidley told reporters on Tuesday that Mr Trump, a Republican, did not mean to be racially insensitive.