Cyclone Mekunu has struck southern Oman, bringing high winds and rain and killing a 12-year-old girl.
Three other people were injured as the cyclone intensified in strength on Friday, flooding roads and submerging vehicles.
Winds of up to 170 km per hour have been reported and thousands of residents near coastal areas have been moved to shelters.
The storm's landfall to the west of Oman's second city Salalah came a day after it hit the Yemeni island of Socotra, where seven people were kiled.
Authorities have told residents to stay inside and Salalah's airport has been closed.