Yemen declared a state of emergency on the island of Socotra on Thursday as a tropical storm intensified after flooding several villages and capsizing boats to leave at least 17 people missing, government officials said.

Socotra, which lies between the Arabian Peninsula and the Horn of Africa, has been largely untouched by Yemen's three-year-old war. It is under the control of the internationally recognized government whose president, Abdu Rabbu Mansour Hadi, is in exile in Saudi Arabia.

The island "requires urgent aid to help people stranded in their villages or those who reside in the mountains," government spokesman Rajeh Badi told state news agency SABA.

He said 17 people were missing after two boats capsized and three cars were washed away by floods. Another official said more than 200 families had been evacuated from their villages.

The storm is worsening and most parts of the island have lost communications, said the governor of the nearby province of Hadramout.

The same weather system hit the Horn of Africa on Wednesday, killing more than 50 people in Somaliland. urn:newsml:reuters.com:*:nL5N1SU0NM

Yemeni government spokesman Badi called on international humanitarian organisations and the Riyadh-led military coalition participating in the war to provide urgent aid to the island, where Saudi and UAE forces have a presence.

The Western-backed coalition intervened in Yemen in 2015 to try to restore Hadi's government, toppled by the Iran-aligned Houthi movement.

The storm is expected to hit southern Yemen and the coast of neighboring Oman on Thursday, Oman's state news agency reported.

It said Omani authorities evacuated hospitals in Dhofar province and other areas bordering Yemen, while the Public Authority for Civil Aviation said the country's second largest airport, in Salalah, would be shut for 24 hours from midnight (2000 GMT).

Yemen is already grappling with one of the world's worst humanitarian crises. The war has killed more than 10,000 people, displaced three million, triggered a cholera outbreak and pushed the impoverished country to the verge of starvation, according to the United Nations.

(Additional reporting by Aziz El Yaakoubi in Dubai and Sarah Dadouch in Riyadh; Editing by Ghaida Ghantous and John Stonestreet) ((aziz.elyaakoubi@thomsonreuters.com; +971552994086)(;))