The Associated Press photograph portrays Obama wearing a white turban and a wraparound white robe presented to him by elders in Wajir, in northeastern Kenya. Obama's estranged late father was Kenyan and Obama visited the country in 2006, attracting thousands of well-wishers.
The gossip and news Web site The Drudge Report posted the photograph Monday and said it was being circulated by "Clinton staffers" and quoted an e-mail from an unidentified campaign aide. Drudge did not include proof of the e-mail in the report.
"I just want to make it very clear that we were not aware of it, the campaign didn't sanction it and don't know anything about it," Clinton spokesman Howard Wolfson said in a teleconference with reporters. "None of us have seen the e-mail in question. If anybody has independent reporting that they've done on it I would welcome it."
Obama, in an interview with WOAI radio in San Antonio, Texas, said voters are "saddened when they see these kind of politics."
"Everybody knows that whether it's me or Senator Clinton or Bill Clinton that when you travel to other countries they ask you to try on traditional garb that you have been given as a gift," he said. "The notion that the Clinton campaign would be trying to circulate this as a negative on the same day that Senator Clinton was giving a speech about how we repair our relationships around the world is sad."
Obama campaign manager David Plouffe accused Clinton's campaign of "the most shameful, offensive fear-mongering we've seen from either party in this election."
Clinton campaign manager Maggie Williams said the Obama campaign's reaction was inflaming passions and distracting voters.
"Enough," Williams said in a statement. "If Barack Obama's campaign wants to suggest that a photo of him wearing traditional Somali clothing is divisive, they should be ashamed. Hillary Clinton has worn the traditional clothing of countries she has visited and had those photos published widely.
"This is nothing more than an obvious and transparent attempt to distract from the serious issues confronting our country today and to attempt to create the very divisions they claim to decry."
In a teleconference with reporters, retired Air Force Gen. Scott Gration, an Obama adviser who accompanied the Illinois senator to Kenya two years ago, said the senator was there to learn how tribes were organizing themselves.
"And in the course of this, Senator Obama was given an outfit and as the guest that he was, the great guest, he took this outfit and they encouraged him to try some of it on," Gration said. "It was a thing that we all do."
In December, two Clinton Iowa volunteers resigned after forwarding a hoax e-mail that falsely said Obama is a Muslim possibly intent on destroying the United States. Obama is a member of the United Church of Christ and says he has never been a Muslim, but false rumors about Islamic ties are circulating on the Internet.