More than half a million people in the Philippines have fled from a powerful typhoon in one of the world's biggest peacetime evacuations as the storm churns toward central provinces that still bear the scars of a supertyphoon 13 months ago.

Typhoon Hagupit was approaching eastern coasts on Saturday, with its eye 230 km (145 miles) east-northeast of Borongan, in Eastern Samar province, the weather bureau PAGASA said.

The storm was downgraded to a notch below supertyphoon category but could still unleash huge destruction with torrential rain and potentially disastrous storm surges of up to 4.5 meters (15 feet).