ADEN, YEMEN: A rare tropical cyclone packing hurricane-force winds killed three people and injured scores on the Yemeni island of Socotra on Monday, residents and officials said, and then headed for an Al Qaeda-controlled town on the mainland.

Amateur pictures and videos on social media, which could not be immediately verified, showed torrents of water washing through the streets of the Socotra provincial capital Hadibu.

"Three people were killed, around 100 have been injured," said a local official, without describing the causes of death.

Mohammed Alarqbi of the Socotra Environment Office said torrential rains had pounded impoverished coastal villages.

"Around 1,500 families have fled to the interior and to the mountains. There's absolutely no help coming from the outside."

Situated in the Arabian Sea and slightly larger than Majorca or Rhode Island, isolated Socotra is home to hundreds of exotic plant species found nowhere else on earth. Its 50,000 residents speak their own language.

Long remote, the island has become especially cut off from mainland Yemen by a seven-month war there between Iran-allied fighters and a coalition of Arab states led by Saudi Arabia.

Yemen, generally arid and hot, receives relatively little rainfall and the infrastructure in the Arabian Peninsula's poorest country is ill-equipped built to handle large deluges.

In an update at 0900 GMT, the UN World Meteorological Organisation said the storm, named Chapala, was an "extremely severe cyclonic storm" with sustained winds of 160-185 kmh (100-115 mph), but would weaken gradually to "very severe" over the next six hours.

Sea conditions around the centre of the storm were "phenomenal", the WMO update said.

Slightly weakened, the storm is expected to hit the mainland on Tuesday morning near the port of Mukalla, which has been run by a tribal council and Al Qaeda militants since the army and government institutions withdrew in April.

One of the militants in the town posted pictures on his Twitter page of a convoy of pickup trucks crudely labelled "rescue team" patrolling the seafront on Sunday night.

"God protect us, the winds are not normal in Mukalla, may the Lord deliver us ... Your prayers, please, O monotheists," said the man, going by the name of Laith al-Mukalla.

He recommended packing flashlights and first aid kits. Other, earlier posts on Twitter showed images of his al Qaeda comrades demolishing the shrines of local saints last week.

The authenticity of the account could not be verified.

Residents worried that Yemen's power vacuum would mean no authorities were in a position to deal with storm damage.

"The sea water level has risen by 9 metres (30 feet) and has destroyed Mukalla's seafront," said resident Muhammed Ba Zuhair. "Many people have left there homes and are seeking refuge in schools. No relief or aid efforts are under way by either the tribal council or al Qaeda, and the situation is really bad."

Forecasts late last week indicated the cyclone would strike the coast close to neighbouring Oman's second city Salalah while avoiding populous areas of Yemen, which has never experienced such a storm. But its latest trajectory takes in southern Yemen, weakening as it bears down on the capital Sanaa in the north.