Tropical Cyclone Shaheen slammed into Oman on Sunday with ferocious winds and heavy rain, flooding streets, prompting evacuations from coastal areas and delaying flights to and from the capital, Muscat.
The death toll from the cyclone rose to five on Monday while other fishermen from Iran remained missing as the storm moved further inland into Oman and weakened.
Authorities in Oman said they found the body of a man who disappeared when floodwaters swept him away from his vehicle.
On Sunday, as the storm made landfall, they said a child similarly drowned and two people died in a landslide.
In Iran, state television said rescuers found the body of one of five fishermen who went missing off Pasabandar, a fishing village near the border with Pakistan.
Earlier on Sunday, Iranian Deputy Parliament Speaker Ali Nikzad said he feared as many as six fishermen had been killed because of the cyclone.
Omani state television broadcast images of flooded roadways and valleys as the storm churned deeper into the sultanate, its outer edges reaching the neighbouring United Arab Emirates which has issued warnings to residents that the storm was coming.