MANILA, Aug 27 (Reuters) - Tropical storm Saola has intensified into a super typhoon, the Philippine weather bureau said on Sunday, raising the possibility of heavy rain and powerful winds hitting important rice and corn growing areas in northern provinces.

Saola, with maximum winds of up to 185 kph near its centre and gusts of up to 230 kph, was over coastal waters of Isabela province early on Sunday, the bureau said in a bulletin.

Heavy rainfall was expected later on Sunday and on Monday in the provinces of Isabela, Cagayan, Ilocos and the mountainous Cordillera region, raising the risk of flooding and landslides, the weather bureau said.

These provinces are among the country's biggest rice, corn and vegetable producers.

Saola was also expected to affect provinces on the main Luzon island as well as the capital, Manila, over the next three days, it said.

Last month, strong winds and rain lashed the northern Philippines as powerful typhoon Doksuri made landfall, causing rivers to overflow and leaving thousands without power.

Doksuri went on to make landfall in China where it left a trail of destruction.

Saola was forecast to turn north on Monday and to make landfall over southern Taiwan late on Wednesday or early Thursday, the weather bureau said.