Veteran rights activist Mohammadi, 51, currently held in Tehran's Evin prison, was awarded the Nobel prize in October "for her fight against the oppression of women in Iran".
"Narges Mohammadi, today, through a message from Evin Prison, has informed her family that she started a hunger strike several
hours ago. We are concerned about Narges Mohammadi's physical condition and health," her family said in a statement.
Mohammadi is refusing under any circumstances to wear a hijab, the head covering which has been obligatory for women in public spaces since shortly after Iran's 1979 Islamic revolution.