Tropical Cyclone Mekunu, which was around 200 km away from Salalah city, was upgraded to category 2 on Friday with wind speeds reaching 70 to 80 knots (126 to 144 km/h), according to the latest weather charts.
Oman News Agency reported that the cyclone will intensify within 12 hours. The forecast indicated that the centre of the tropical cyclone was approaching the coasts of the Dhofar governorate, leading to heavy rains and flooding.
Oman's second-biggest airport, Salalah, will remain closed through Saturday as the cyclone bears down on the coast of Oman, national authorities announced.
The sea state will be rough along the coasts of Dhofar and Al-Wusta governorates, with maximum wave height between 8 and 12 metres.
The Public Authority for Civil Aviation advised people to follow the weather bulletins and guard against flash floods, apart from avoiding the sea.
Salalah airport was initially closed at midnight on Thursday due to the powerful storm, which had already struck neighbouring Yemen.
On Friday, the civil aviation authority said the airport shutdown had been extended for 24 more hours.
Flights in the Omani areas affected by the cyclone are being rerouted, the agency added on its Twitter feed.
On Friday, the cyclone was nearing Oman's coastal province of Dhofar, of which Salalah is the capital city.
Authorities have evacuated areas in Dhofar and other parts near the border with war-wracked Yemen to safer shelter centres, Dubai-based broadcaster Al Arabiya reported.
This week, Mekunu struck the Yemeni island of Socotra, causing havoc and leaving at least 19 people missing in ship and car mishaps there, according to government officials.
The Indian Ocean island, recognised by Unesco as a world natural heritage site, is famous for its rich biodiversity.