Democrat Barack Obama is fighting back against cyber attacks and innuendo with a website that seeks to debunk Internet rumors, most notably a claim his wife used a racial epithet during a church talk and assertions that he is a Muslim.

Obama, who is the first African-American to win a major party's nomination for the White House, faces problems new to US presidential politics in a country burdened with a history of racism.

The Internet move is an unusual one in American politics, where candidates routinely ignore fabricated negative stories about them - unless they reach a boil - rather than risk giving them more publicity with explanations or denials.