'Black' head of US civil rights group resigns amid allegations

A US civil rights activist has resigned from the leadership of a leading African American advocacy group, amid a "firestorm" over allegations that she was a white person who masqueraded for years as black.

The Washington state chapter of the National Association for the Advancement of Colored People (NAACP), posted Rachel Dolezal's resignation letter on its Facebook page on Monday.

In it, she writes that her commitment to the "racial and social justice movement" is undiminished but that "the dialogue has unexpectedly shifted internationally to my personal identity in the context of defining race and ethnicity."

Dolezal, 37, built a career as an activist in the black community of Spokane, Washington.

She rose to become the president of the city's branch of the NAACP and served as an independent mediator for the city's police force.

Neither position required that she be black, but media reports said Dolezal identified herself in application forms as black.

She apparently resigned under pressure from the civil rights group.

"I have always deferred to the state and national NAACP leadership and offer my sincere gratitude for their unwavering support of my leadership through this unexpected firestorm," Dolezal wrote.

Her parents, who are both white, said their daughter is as well, providing local media with a birth certificate and photographs of a Dolezal - who now appears tawny skinned and dark haired - as a blonde, fair-skinned child.