With thousands more feared missing.
Storm Daniel swept in over the Mediterranean on Sunday after pummelling Greece last week.
One official said dams above Derna collapsed, sweeping away whole neighborhoods.
The disaster took place in a part of the country that the internationally-recognized government in Tripoli does not control.
Still, the council in Tripoli which serves as head of state in the divided country has called for international help.
Turkey, for one, said it is sending three planes to transport rescuers and humanitarian aid.
Earlier on Monday, the head of the Red Crescent aid group in the region said the death toll was expected to hit 250.
Reuters could not immediately verify either estimate.
Authorities from the interim government in Tripoli and in the east have both declared three days of mourning.
