SYDNEY, Feb 7 (Reuters) - Ports in Western Australia, including the world's biggest iron-ore export hub, were closed on Saturday as a tropical cyclone developed off the coast from the vast Pilbara iron ore region, the ports' operator said.

Tropical cyclone Mitchell, a category 2 storm, sparked the closure of Port Hedland, as well as the ports of Ashburton, Cape Preston West, Dampier and Varanus Island, Pilbara Ports said in an online alert.

The cyclone "will most likely begin to make a gradual turn to the southwest and then south from tonight, and in doing so move closer to the coast," the operator said, referring to the Pilbara, a remote resource-rich area twice the size of the United Kingdom.

Mitchell, intensifying on Saturday, was forecast to become a category 3 cyclone overnight that could bring very destructive wind gusts of up to 170 kph (105 mph) to the Pilbara, Australia's weather bureau said on its website.

Port Hedland, about 1,300 km (800 miles) north of Western Australia's state capital, Perth, is the world's biggest export point for iron ore and is used by miners including BHP Group, Fortescue and billionaire Gina Rinehart's Hancock Prospecting.

On Friday, Pilbara Ports said its ports were being cleared due to emerging cyclone risk.

(Reporting by Sam McKeith in Sydney; Editing by William Mallard)

((Samuel.McKeith@thomsonreuters.com;))