Yahoo said that it had fired David Chalian, the website's Washington bureau chief, after he was recorded at the Republican National Convention saying that convention officials were "happy to have a party with black people drowning".
Yahoo said the reference Mr Chalian made to the flooding caused by Hurricane Isaac was "inappropriate and does not represent the views" of the company.
In a statement, Yahoo also said: "We have already reached out to the Romney campaign, and we apologise to Mitt Romney, his staff, their supporters and anyone who was offended."
Mr Chalian said he was profoundly sorry for making what he called "an inappropriate and thoughtless joke".
He publicly apologised to the Romneys.
Mr Chalian's "drowning" comment was made Monday night during Yahoo's live Web video coverage of the convention.
The coverage is being produced in partnership with ABC News, where Mr Chalian worked as political director until 2010. After a little more than a year at PBS NewsHour, he joined Yahoo in late 2011.
The comment was picked up by NewsBusters, a conservative media watchdog website, which posted a short video clip of it yesterday morning.
Mr Chalian, who is heard but not seen in the clip, was apparently unaware that his words were being webcast at the time.
In a statement, Mr Chalian said that he was "commenting on the challenge of staging a convention during a hurricane and about campaign optics".
He continued: "I have apologised to the Romney campaign, and I want to take this opportunity to publicly apologise to Governor and Mrs Romney. I also regret causing any distraction from the exceptional coverage of the Republican convention by Yahoo News and ABC News."
New York Times