The National Transitional Council in Libya says Colonel Muammar Gaddafi may be hiding in a remote and thinly populated area surrounded by mountains.
The NTC says he may be moving around a prism of the southern deserts straddling Libya, Algeria and Niger.
Colonel Gaddafi has been on the run since NTC forces surged into Tripoli late August.
His daughter and several other family members fled to Algeria two months ago.
NTC officials have made capturing Colonel Gaddafi and his family and putting them on trial a priority.