Federal Reserve Board Chairman Janet Yellen holds her monthly news conference at the Federal Reserve, September 17, 2014 in Washington, DC

US Federal Reserve chief Janet Yellen said Friday she is greatly concerned over the widening gap between the rich and poor in the United States.

Speaking in the US city of Boston, Yellen said "income and wealth inequality are near their highest levels in the past hundred years" and have widened during the economic recovery.

AFP