An American PR executive has sparked a Twitter storm with an apparently racist tweet ahead of a trip to Africa.

The now-deleted tweet, posted from the account of Justine Sacco, went viral and was branded "outrageous" by her employer.

It said:

Sacco is the corporate communications director for IAC, which owns popular websites OkCupid, Match.com, CollegeHumor, The Daily Beast and Vimeo.

With her flight to South Africa apparently airborne, and Sacco possibly unaware of the furore she had created, the hashtag #hasjustinelandedyet trended, while her account appeared to have been deleted.

But IAC were aware, and a spokesman told the International Business Times: "This is an outrageous, offensive comment that does not reflect the views and values of IAC.

"Unfortunately, the employee in question is unreachable on an international flight, but this is a very serious matter and we are taking appropriate action."