With just one tweet, media mogul Rupert Murdoch managed to raise doubts on US President Barack Obama's credibility as a "black president," offending many Twitter users.

On his personal Twitter account (@rupertmurdoch), Murdoch wrote: "Ben and Candy Carson terrific. What about a real black President who can properly address the racial divide? And much else."

Murdoch was raving about Republican presidential hopeful and neurosurgeon Dr. Ben Carson, but little did he know that his tweet would generate tons of negative comments and sarcastic remarks.

Actor Harry Shearer did not seem pleased with Murdoch's tweet and replied, "Can you please regularly advise black Americans on which of them is 'real,' so they'll be free of doubt?"

Stephen Mayne tweeted, "Oh dear @rupertmurdoch, you are going to get flogged for suggesting Barack Obama is not 'a real black president.' You need a Twitter editor!" Simon Royal added, "Or an off switch, or good manners, or not talking about stuff you don't understand..."

Others wanted to understand what a "real black president" means to Murdoch, while several others suggested that he simply delete his Twitter account.

"How do you define 'real black', Rupert? Are we back in your 30s childhood, in the era of 'half-castes' and 'mulattoes'?" questioned Mark Colvin.

A Twitter user named Tracy, meanwhile, said Murdoch's financial success does not guarantee him proper wits. "Who knew that the more money you make, the smaller your brain shrinks. Murdoch is living proof," she wrote.

After receiving an overwhelming amount of backlash, Murdoch tweeted an apology 11 hours later and explained that he did not mean to upset people. "Apologies! No offence meant. Personally find both men charming."

Murdoch, 84, is the owner of Fox News Channel and other media brands such as the Fox broadcast network and the FX cable channel. He is also the co-executive chairman of 21st Century Fox, but he recently passed down his job to his son James.

When sought for comments about Murdoch's controversial tweet, a 21st Century Fox spokeswoman declined to give any. "We don't comment on his tweets," she simply said.