Media mogul Rupert Murdoch has suggested US president Barack Obama is not a "real black president".

The 84-year-old founder of the News Corp media empire was praising black Republican presidential candidate Ben Carson and his wife on Twitter when he wrote: "Ben and Candy Carson terrific. What about a real black President who can properly address the racial divide?"

Later, Mr Murdoch recommended a New York magazine article asking whether Mr Obama has done enough for the African-American community.

Mr Murdoch, who founded Fox News Channel, has praised retired neurosurgeon Mr Carson on Twitter before, calling him "irreproachable on background, achievements, character, vision".

As well as US publications The New York Post and The Wall Street Journal, his media empire includes The Times and The Sun in the UK.