* Tens of thousands more people may need to moved
* Storm surges up to 6 metres possible
* Mangkhut due to arrive early hours of Saturday
* Category 5 storm strongest to hit country this year (Recast, adds details, comments, new estimated arrival time)
By Enrico Dela Cruz
MANILA, Sept 14 (Reuters) - Philippine authorities evacuated more areas on Friday and warned an estimated 5.2 million people in the path of a "very destructive" typhoon to stay indoors, as the country braced for heavy rain and damage to infrastructure and crops.
Super Typhoon Mangkhut is expected to barrel through the northernmost tip of the Philippines Saturday morning, carrying 205 kph wind speeds, and gusts of up to 255 kph, that it has maintained since it struck Micronesia earlier in the week.
More than 9,000 people have been moved to temporary shelters as Mangkhut, locally known as Ompong, makes its way towards the rice- and corn-producing provinces of Cagayan and Isabela where it is forecast to make landfall overnight. Disaster officials warned that tens of thousands more may need to be moved and weather forecasters warned of storm surges as high as six metres in coastal villages in the typhoon's path. Second and third contingents of rescue teams were being prepared, in case first-responders get into trouble themselves.
"My appeal is that we need to heed the advice of the authorities. Stay indoors," said presidential adviser Francis Tolentino, the government's disaster response coordinator.
The storm further picked up speed and was about 340 km east of the Philippines late afternoon on Friday. Video posted on social media by Cagayan residents showed trees being whipped by fierce winds under dark grey skies as rain lashed down on buildings.
Cagayan Governor Manuel Mamba said he expects widespread damage to crops and infrastructure in his province, and said help would be needed to rebuild.
"Last time we had a super typhoon, there were 14,000-plus of totally destroyed houses and about 40,000-plus of partially destroyed houses," he told news channel ANC.
"We expect this kind of damage with a super typhoon like this and so we would ask the assistance of the national government and even the private sector."
The capital, Manila, and more than three dozen northern and central provinces have been placed under storm warning signals. Classes have been suspended and government offices shut early in more than 600 places, while military, medical and emergency response teams were put on stand by.
The coastguard said about 5,000 passengers were stranded at several ports by the impending storm, which will head on towards Hong Kong, China and Vietnam.
Mangkhut's peak winds are stronger than those of Hurricane Florence, which has left 188,000 without power and is expected to drop eight months of rain on the Carolinas in the United States.
"The concerns here are landslides and infrastructure being washed away," said Junie Cua, governor of Quirino province on the main island of Luzon.
Authorities are taking extra precautions as they draw comparison with Typhoon Haiyan, which devastated central areas of the archipelago in 2013, and killed 6,300 people, many in storm surges that reached as high as eight metres.
But weather forecasters said Mangkhut's wind speed was unlikely to accelerate further from the current 205 kph and reach Haiyan's 240 kph. Northern Luzon is also less densely populated.
Mangkhut might slightly weaken after landfall but could still be "very destructive", said Rene Paciente, assistant chief at the weather bureau.
Crop damage in a worst-case scenario could reach about 157,000 tonnes of paddy rice and about 257,000 tonnes of corn, worth 13.5 billion pesos ($250 million), the agriculture ministry said.
That could result in tightness in the domestic rice supplies at a time when retail prices are already high, compounding worries about inflation.
(Writing by Martin Petty and Enrico dela Cruz)
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