Media mogul Rupert Murdoch has apologised after suggesting on Twitter that Barack Obama is not a "real black President" of the United States.

The 84-year-old posted two messages after Ben Carson, the African-American Republican 2016 presidential candidate, appeared on The Kelly File show on Murdoch's US Fox News network.

In them, Mr Murdoch, whose News Corporation empire includes the Sun and Times newspapers and Sky television in the UK, said: "Ben and (his wife) Candy Carson terrific. What about a real black President who can properly address the racial divide? And much else.

"Read New York magazine for minority community disappointment with POTUS (President Of The United States)."

The comments attracted criticism on the social media network, including from Simpsons and Spinal Tap actor Harry Shearer, who replied: "Can you please regularly advise black Americans on which of them is 'real', so they'll be free of doubt?"

Later Mr Murdoch wrote: "Apologies! No offence meant. Personally find both men charming."

Mr Murdoch has championed Mr Carson on the social media platform previously, calling him "humble but tough. A real vision for a great America again" a month ago.