NEW YORK: Barack Obama's bid to become the first black American president could have taken a blow with the revelation that his aunt was an illegal immigrant in the US.

News about Zeituni Onyango, 56, just three days before election is a chance for Republican presidential candidate John McCain to generate some last-minute negative headlines about Obama.

But Obama has denied having any knowledge about his aunt living in the US illegally, and said laws covering the case should be adhered to. A statement given to the Associated Press (AP) by Obama's campaign said: "Senator Obama has no knowledge of her status but obviously believes that any and all appropriate laws be followed."